chore: release 0.120.21 (#484)

🤖 I have created a release \*beep\* \*boop\*
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### [0.120.21](https://www.github.com/googleapis/java-errorreporting/compare/v0.120.20...v0.120.21) (2021-04-09)


### Dependencies

* update dependency com.google.cloud:google-cloud-core to v1.94.6 ([#483](https://www.github.com/googleapis/java-errorreporting/issues/483)) ([31852b4](https://www.github.com/googleapis/java-errorreporting/commit/31852b4cbd87c47b578f30c8a0e2fd016bf44161))
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This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).

errorreporting/snapshot/pom.xml

@@ -28,7 +28,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-errorreporting</artifactId>
-      <version>0.120.38-beta-SNAPSHOT</version>
+      <version>0.120.38-beta</version>
     </dependency>
     <!-- {x-version-update-end} -->