match test protoc & grpc plugin versions to gapic

Change-Id: I8597dddd20d836afdfec6a9eee94310073ef5edf

Author: igorbernstein2

google-cloud-bigtable/pom.xml

@@ -45,8 +45,8 @@
     <bigtable.cfe-data-batch-endpoint>batch-bigtable.googleapis.com:443</bigtable.cfe-data-batch-endpoint>
 
     <!-- These are needed to compile the protobuf used by Changestream merging acceptance test. -->
-    <test-protoc-grpc.version>1.79.0</test-protoc-grpc.version>
-    <test-protoc.version>4.33.5</test-protoc.version>
+    <test-protoc-grpc.version>1.76.3</test-protoc-grpc.version>
+    <test-protoc.version>4.33.2</test-protoc.version>
   </properties>
 
   <dependencyManagement>