chore: build: update minimum go version to 1.21.7 (#11652)

Now that 1.22 is out. Libp2p will also be dropping support for 1.20
soon (if it hasn't already?) so it can _finally_ stop supporting
specific compiler versions (we can stop caring so much about the
"maximum" supported go version).

.circleci/config.yml

@@ -7,12 +7,12 @@ executors:
   golang:
     docker:
       # Must match GO_VERSION_MIN in project root
-      - image: cimg/go:1.20.7
+      - image: cimg/go:1.21.7
     resource_class: medium+
   golang-2xl:
     docker:
       # Must match GO_VERSION_MIN in project root
-      - image: cimg/go:1.20.7
+      - image: cimg/go:1.21.7
     resource_class: 2xlarge
   ubuntu:
     docker:
@@ -164,7 +164,7 @@ jobs:
         default: unit
         description: Test suite name to report to CircleCI.
     docker:
-      - image: cimg/go:1.20
+      - image: cimg/go:1.21
         environment:
           LOTUS_HARMONYDB_HOSTS: yugabyte
       - image: yugabytedb/yugabyte:2.18.0.0-b65
@@ -218,7 +218,7 @@ jobs:
           test with. If empty (the default) the commit defined by the git
           submodule is used.
     docker:
-      - image: cimg/go:1.20
+      - image: cimg/go:1.21
     resource_class: << parameters.resource_class >>
     steps:
       - install-ubuntu-deps
@@ -412,7 +412,7 @@ jobs:
         description: |
           Arguments to pass to golangci-lint
     docker:
-      - image: cimg/go:1.20
+      - image: cimg/go:1.21
     resource_class: medium+
     steps:
       - install-ubuntu-deps

.circleci/template.yml

@@ -7,12 +7,12 @@ executors:
   golang:
     docker:
       # Must match GO_VERSION_MIN in project root
-      - image: cimg/go:1.20.7
+      - image: cimg/go:1.21.7
     resource_class: medium+
   golang-2xl:
     docker:
       # Must match GO_VERSION_MIN in project root
-      - image: cimg/go:1.20.7
+      - image: cimg/go:1.21.7
     resource_class: 2xlarge
   ubuntu:
     docker: