test(deps): update dependency com.google.protobuf:protoc to v4

Author: renovate-bot

google-cloud-bigtable/pom.xml

@@ -39,7 +39,7 @@
 
     <!-- These are needed to compile the protobuf used by Changestream merging acceptance test. -->
     <test-protoc-grpc.version>1.61.1</test-protoc-grpc.version>
-    <test-protoc.version>3.25.3</test-protoc.version>
+    <test-protoc.version>4.26.1</test-protoc.version>
   </properties>
 
   <dependencyManagement>