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

testing/ef_tests/src/cases/fork_choice.rs

@@ -1039,11 +1039,9 @@ impl<E: EthSpec> Tester<E> {
 
     pub fn check_head_payload_status(&self, expected_status: u8) -> Result<(), Error> {
         let head = self.find_head()?;
-        check_equal(
-            "head_payload_status",
-            head.head_payload_status() as u8,
-            expected_status,
-        )
+        // PayloadStatus repr: Empty=0, Full=1, Pending=2 (matches spec constants).
+        let actual = head.head_payload_status() as u8;
+        check_equal("head_payload_status", actual, expected_status)
     }
 
     pub fn check_should_override_fcu(