Re-enable shutdown stalled test (#106498)

NodeShutdownIT.testStalledShardMigrationProperlyDetected has been muted
for a couple years. It apparently reproduced when the failure first
started, but no longer reproduces on main. This commit re-enables the
test and closes the test issue. We can open a new issue with any
subsequent failure.

closes #77456

x-pack/plugin/shutdown/qa/multi-node/src/javaRestTest/java/org/elasticsearch/xpack/shutdown/NodeShutdownIT.java

@@ -291,7 +291,6 @@ public class NodeShutdownIT extends ESRestTestCase {
         ensureGreen(indexName);
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/77456")
     public void testStalledShardMigrationProperlyDetected() throws Exception {
         String nodeIdToShutdown = getRandomNodeId();
         int numberOfShards = randomIntBetween(1, 5);