deps: update dependency com.google.protobuf:protobuf-java to v3.11.4

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| com.google.protobuf:protobuf-java | patch | `3.11.3` -> `3.11.4` |

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pom.xml

@@ -69,7 +69,7 @@
     <google.auth.version>0.20.0</google.auth.version>
     <gax.version>1.53.1</gax.version>
     <grpc.version>1.27.0</grpc.version>
-    <protobuf.version>3.11.3</protobuf.version>
+    <protobuf.version>3.11.4</protobuf.version>
     <junit.version>4.13</junit.version>
     <guava.version>28.2-android</guava.version>
     <threeten.version>1.4.1</threeten.version>