[TEST] Exclude name on ScriptContextInfo mutate (#50332) (#50337)

ScriptContextInfoSerializingTests:testEqualsAndHashcode was failing
because the mutation was generating the same name.

**Backport**

Fixes: #50331

Author: stu-elastic

server/src/test/java/org/elasticsearch/action/admin/cluster/storedscripts/ScriptContextInfoSerializingTests.java

@@ -56,7 +56,10 @@ protected ScriptContextInfo mutateInstance(ScriptContextInfo instance) throws IO
     }
 
     private static ScriptContextInfo mutate(ScriptContextInfo instance, Set<String> names) {
-        if (names == null) { names = new HashSet<>(); }
+        if (names == null) {
+            names = new HashSet<>();
+            names.add(instance.name);
+        }
         switch (randomIntBetween(0, 2)) {
             case 0:
                 return new ScriptContextInfo(