fix: revert changes in opencensus

Author: diegomarquezp

gax-java/gax/src/main/java/com/google/api/gax/tracing/OpencensusTracer.java

@@ -406,14 +406,6 @@ public void responseReceived() {
     totalReceivedMessages++;
   }
 
-  /** {@inheritDoc} */
-  @Override
-  public void recordResponseSize(long responseSize) {
-    span.putAttribute(
-        ObservabilityAttributes.HTTP_RESPONSE_BODY_SIZE,
-        AttributeValue.longAttributeValue(responseSize));
-  }
-
   /** {@inheritDoc} */
   @Override
   public void requestSent() {