Fix test review issues

- Remove wrong latest_message assertions from payload attestation test
  (on_payload_attestation writes to PTC bitfields, not vote tracker)
- Fix corrupted comment: "votes.gloas_enabled() to the genesis block"
  → "votes to the genesis block"
- Fix http_api test fallback string: "n/a" → "irrelevant" to match
  production code
- Add issue link to #[ignore] test
- Add comment explaining head_payload_status as u8 cast

consensus/fork_choice/src/fork_choice.rs

@@ -1285,7 +1285,7 @@ where
         //  2. Ignore all attestations to the zero hash.
         //
         // (1) becomes weird once we hit finality and fork choice drops the genesis block. (2) is
-        // fine because votes.gloas_enabled() to the genesis block are not useful; all validators implicitly attest
+        // fine because votes to the genesis block are not useful; all validators implicitly attest
         // to genesis just by being present in the chain.
         if attestation.data().beacon_block_root == Hash256::zero() {
             return Ok(());