deps: update dependency com.google.protobuf:protobuf-bom to v3.18.1 (#583)

Author: renovate-bot

pom.xml

@@ -159,7 +159,7 @@
     <google.api.version>1.32.1</google.api.version>
     <google.http.version>1.40.0</google.http.version>
     <grpc.version>1.41.0</grpc.version>
-    <protobuf.version>3.17.3</protobuf.version>
+    <protobuf.version>3.18.1</protobuf.version>
     <opencensus.version>0.28.0</opencensus.version>
     <annotations-api.version>1.3.2</annotations-api.version>
     <guava.version>31.0.1-jre</guava.version>