deps: adding error prone annotations to dependencyManagement

[suztomo]

"ci / dependencies" was failing in this repository due to the error prone annotation version between Guava and Truth.

[INFO] --- maven-enforcer-plugin:3.0.0-M3:enforce (enforce-maven) @ google-http-client ---
Warning:  Rule 2: org.apache.maven.plugins.enforcer.RequireUpperBoundDeps failed with message:
Failed while enforcing RequireUpperBoundDeps. The error(s) are [
Require upper bound dependencies error for com.google.errorprone:error_prone_annotations:2.3.4 paths to dependency are:
+-com.google.http-client:google-http-client:1.38.2-SNAPSHOT
  +-com.google.guava:guava:30.1-android
    +-com.google.errorprone:error_prone_annotations:2.3.4
and
+-com.google.http-client:google-http-client:1.38.2-SNAPSHOT
  +-com.google.guava:guava-testlib:30.1-android
    +-com.google.errorprone:error_prone_annotations:2.3.4
and
+-com.google.http-client:google-http-client:1.38.2-SNAPSHOT
  +-com.google.truth:truth:1.1.2
    +-com.google.errorprone:error_prone_annotations:2.5.1
]

---

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Fixes #1276 ☕️

[suztomo]

"ci / dependencies" succeeded:

[elharo]

dupes #1268

[suztomo]

@elharo Thank you.