docs: Improve markdownlint configuration (#11104)

## Description

Closes: #9404



---

### Author Checklist

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please add links to any relevant follow up issues.*

I have...

- [x] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [x] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
- [x] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [x] reviewed "Files changed" and left comments if necessary
- [x] confirmed all CI checks have passed

### Reviewers Checklist

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I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

docs/ibc/upgrades/README.md

@@ -4,7 +4,7 @@ parent:
   order: 3
 -->
 
-### Upgrading IBC Chains Overview
+# Upgrading IBC Chains Overview
 
 This directory contains information on how to upgrade an IBC chain without breaking counterparty clients and connections.
 

docs/ibc/upgrades/quick-guide.md

@@ -8,7 +8,7 @@ Learn how to upgrade your chain and counterparty clients. {synopsis}
 
 The information in this doc for upgrading chains is relevant to Cosmos SDK chains. However, the guide for counterparty clients is relevant to any Tendermint client that enables upgrades.
 
-### IBC Client Breaking Upgrades
+## IBC Client Breaking Upgrades
 
 IBC-connected chains must perform an IBC upgrade if their upgrade will break counterparty IBC clients. The current IBC protocol supports upgrading tendermint chains for a specific subset of IBC-client-breaking upgrades. Here is the exhaustive list of IBC client-breaking upgrades and whether the IBC protocol currently supports such upgrades.
 
@@ -26,7 +26,7 @@ Note: Since upgrades are only implemented for Tendermint clients, this doc only
 8. Upgrading to a non-backwards compatible version of IBC: **Unsupported**, as IBC version is negotiated on connection handshake.
 9. Changing the Tendermint LightClient algorithm: **Partially Supported**. Changes to the light client algorithm that do not change the ClientState or ConsensusState struct may be supported, provided that the counterparty is also upgraded to support the new light client algorithm. Changes that require updating the ClientState and ConsensusState structs themselves are theoretically possible by providing a path to translate an older ClientState struct into the new ClientState struct; however this is not currently implemented.
 
-### Step-by-Step Upgrade Process for Cosmos SDK chains
+## Step-by-Step Upgrade Process for Cosmos SDK chains
 
 If the IBC-connected chain is conducting an upgrade that will break counterparty clients, it must ensure that the upgrade is first supported by IBC using the list above and then execute the upgrade process described below in order to prevent counterparty clients from breaking.
 
@@ -37,7 +37,7 @@ Upon the `UpgradeProposal` passing, the upgrade module will commit the UpgradedC
 
 Once the chain reaches the upgrade height and halts, a relayer can upgrade the counterparty clients to the last block of the old chain. They can then submit the proofs of the `UpgradedClient` and `UpgradedConsensusState` against this last block and upgrade the counterparty client.
 
-### Step-by-Step Upgrade Process for Relayers Upgrading Counterparty Clients
+## Step-by-Step Upgrade Process for Relayers Upgrading Counterparty Clients
 
 Once the upgrading chain has committed to upgrading, relayers must wait till the chain halts at the upgrade height before upgrading counterparty clients. This is because chains may reschedule or cancel upgrade plans before they occur. Thus, relayers must wait till the chain reaches the upgrade height and halts before they can be sure the upgrade will take place.