Run grizzly-http muzzle on Java 21 (#11241)

Grizzly 5.0.1+ requires Java 21 to load. Bump the muzzle directive's
javaVersion to 21 so the AssertPass check for 5.0.1 succeeds, and
document why 5.0.0 is skipped (broken POM referencing
grizzly-bom:5.0.0-SNAPSHOT).

Author: smola

dd-java-agent/instrumentation/grizzly/grizzly-http-2.3.20/build.gradle

@@ -3,8 +3,10 @@ muzzle {
     group = "org.glassfish.grizzly"
     module = 'grizzly-http'
     versions = "[2.3.20,)"
-    javaVersion = '11'
+    // Grizzly 5.0.1+ requires Java 21 to load.
+    javaVersion = '21'
     assertInverse = false
+    // 5.0.0 has a broken POM (references grizzly-bom:5.0.0-SNAPSHOT) and cannot be resolved.
     skipVersions += "5.0.0"
   }
 }