Ignore flaky sampling test (#6326)

* Ignore flaky sampling test.

beacon_node/network/src/sync/block_lookups/tests.rs

@@ -1967,6 +1967,7 @@ fn sampling_happy_path() {
 }
 
 #[test]
+#[ignore] // Ignoring due to flakiness https://github.com/sigp/lighthouse/issues/6319
 fn sampling_with_retries() {
     let Some(mut r) = TestRig::test_setup_after_peerdas() else {
         return;