Deprecate exchangeTransitionConfiguration functionality (#4517)

## Issue Addressed

Solves #4442 
## Proposed Changes

EL clients log errors if we don't query this endpoint, but they are making releases that remove this error logging. After those are out we can stop calling it, after which point EL teams will remove the endpoint entirely. 
Refer https://hackmd.io/@n0ble/deprecate-exchgTC

beacon_node/beacon_chain/src/merge_readiness.rs

@@ -86,9 +86,6 @@ pub enum MergeReadiness {
         #[serde(serialize_with = "serialize_uint256")]
         current_difficulty: Option<Uint256>,
     },
-    /// The transition configuration with the EL failed, there might be a problem with
-    /// connectivity, authentication or a difference in configuration.
-    ExchangeTransitionConfigurationFailed { error: String },
     /// The EL can be reached and has the correct configuration, however it's not yet synced.
     NotSynced,
     /// The user has not configured this node to use an execution endpoint.
@@ -109,12 +106,6 @@ impl fmt::Display for MergeReadiness {
                     params, current_difficulty
                 )
             }
-            MergeReadiness::ExchangeTransitionConfigurationFailed { error } => write!(
-                f,
-                "Could not confirm the transition configuration with the \
-                    execution endpoint: {:?}",
-                error
-            ),
             MergeReadiness::NotSynced => write!(
                 f,
                 "The execution endpoint is connected and configured, \
@@ -155,14 +146,6 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
     /// Attempts to connect to the EL and confirm that it is ready for the merge.
     pub async fn check_merge_readiness(&self) -> MergeReadiness {
         if let Some(el) = self.execution_layer.as_ref() {
-            if let Err(e) = el.exchange_transition_configuration(&self.spec).await {
-                // The EL was either unreachable, responded with an error or has a different
-                // configuration.
-                return MergeReadiness::ExchangeTransitionConfigurationFailed {
-                    error: format!("{:?}", e),
-                };
-            }
-
             if !el.is_synced_for_notifier().await {
                 // The EL is not synced.
                 return MergeReadiness::NotSynced;