deps: revert protobuf to 3.19 (#2035)

Reverting update dependency com.google.protobuf:protobuf-java to v3.20.0 (#2029)

This reverts commit b36c162.

Author: suztomo

pom.xml

@@ -499,7 +499,7 @@
     <project.oauth.version>1.33.2</project.oauth.version>
     <project.jsr305.version>3.0.2</project.jsr305.version>
     <project.gson.version>2.8.6</project.gson.version>
-    <project.protobuf-java.version>3.20.0</project.protobuf-java.version>
+    <project.protobuf-java.version>3.19.4</project.protobuf-java.version>
     <project.guava.version>31.1-jre</project.guava.version>
     <project.appengine.version>2.0.4</project.appengine.version>
     <project.xpp3.version>1.1.4c</project.xpp3.version>