deps: revert protobuf to 3.19"

This reverts commit 19202bc.

Author: suztomo

pom.xml

@@ -160,7 +160,7 @@
     <google.http.version>1.41.7</google.http.version>
     <graalvm.version>22.0.0.2</graalvm.version>
     <grpc.version>1.45.1</grpc.version>
-    <protobuf.version>3.20.0</protobuf.version>
+    <protobuf.version>3.19.4</protobuf.version>
     <opencensus.version>0.31.0</opencensus.version>
     <annotations-api.version>1.3.2</annotations-api.version>
     <guava.version>31.1-jre</guava.version>