Remove unnecessary override from test

Author: DonalEvans

x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/googlevertexai/completion/GoogleVertexAIChatCompletionServiceSettingsTests.java

@@ -7,7 +7,6 @@
 
 package org.elasticsearch.xpack.inference.services.googlevertexai.completion;
 
-import org.elasticsearch.TransportVersion;
 import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.xpack.inference.services.ConfigurationParseContext;
 import org.elasticsearch.xpack.inference.services.InferenceSettingsTestCase;
@@ -37,12 +36,4 @@ protected GoogleVertexAiChatCompletionServiceSettings createTestInstance() {
             new RateLimitSettings(randomIntBetween(1, 1000))
         );
     }
-
-    @Override
-    protected GoogleVertexAiChatCompletionServiceSettings mutateInstanceForVersion(
-        GoogleVertexAiChatCompletionServiceSettings instance,
-        TransportVersion version
-    ) {
-        return instance;
-    }
 }