deps: update dependency com.google.code.gson:gson to v2.8.7 (#461)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| com.google.code.gson:gson | `2.8.6` -> `2.8.7` | [![age](https://badges.renovateapi.com/packages/maven/com.google.code.gson:gson/2.8.7/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.code.gson:gson/2.8.7/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.code.gson:gson/2.8.7/compatibility-slim/2.8.6)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.code.gson:gson/2.8.7/confidence-slim/2.8.6)](https://docs.renovatebot.com/merge-confidence/) |

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pom.xml

@@ -170,7 +170,7 @@
     <threetenbp.version>1.5.1</threetenbp.version>
     <objenesis.version>2.6</objenesis.version>
     <errorprone.version>2.7.1</errorprone.version>
-    <gson.version>2.8.6</gson.version>
+    <gson.version>2.8.7</gson.version>
   </properties>
 
   <dependencyManagement>