Ensure validator/blinded_blocks/{slot} endpoint conforms to spec (#3429)

## Issue Addressed

#3418

## Proposed Changes

- Remove `eth/v2/validator/blinded_blocks/{slot}` as this endpoint does not exist in the spec.
- Return `version` in the `eth/v1/validator/blinded_blocks/{slot}` endpoint.

## Additional Info

Since this removes the `v2` endpoint, this is *technically* a breaking change, but as this does not exist in the spec users may or may not be relying on this.

Depending on what we feel is appropriate, I'm happy to edit this so we keep the `v2` endpoint for now but simply bring the `v1` endpoint in line with `v2`.

beacon_node/http_api/src/lib.rs

@@ -1988,7 +1988,7 @@ pub fn serve<T: BeaconChainTypes>(
         );
 
     // GET validator/blinded_blocks/{slot}
-    let get_validator_blinded_blocks = any_version
+    let get_validator_blinded_blocks = eth_v1
         .and(warp::path("validator"))
         .and(warp::path("blinded_blocks"))
         .and(warp::path::param::<Slot>().or_else(|_| async {
@@ -2001,8 +2001,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::query::<api_types::ValidatorBlocksQuery>())
         .and(chain_filter.clone())
         .and_then(
-            |endpoint_version: EndpointVersion,
-             slot: Slot,
+            |slot: Slot,
              query: api_types::ValidatorBlocksQuery,
              chain: Arc<BeaconChain<T>>| async move {
                 let randao_reveal = query.randao_reveal.as_ref().map_or_else(
@@ -2044,7 +2043,8 @@ pub fn serve<T: BeaconChainTypes>(
                     .to_ref()
                     .fork_name(&chain.spec)
                     .map_err(inconsistent_fork_rejection)?;
-                fork_versioned_response(endpoint_version, fork_name, block)
+                // Pose as a V2 endpoint so we return the fork `version`. 
+                fork_versioned_response(V2, fork_name, block)
                     .map(|response| warp::reply::json(&response))
             },
         );