Bump gson from 2.9.0 to 2.9.1

Bumps [gson](https://github.com/google/gson) from 2.9.0 to 2.9.1.
- [Release notes](https://github.com/google/gson/releases)
- [Changelog](https://github.com/google/gson/blob/master/CHANGELOG.md)
- [Commits](google/gson@gson-parent-2.9.0...gson-parent-2.9.1)

---
updated-dependencies:
- dependency-name: com.google.code.gson:gson
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

approvaltests-tests/pom.xml

@@ -82,7 +82,7 @@
         <dependency>
             <groupId>com.google.code.gson</groupId>
             <artifactId>gson</artifactId>
-            <version>2.9.0</version>
+            <version>2.9.1</version>
         </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>

approvaltests-util-tests/pom.xml

@@ -49,7 +49,7 @@
         <dependency>
             <groupId>com.google.code.gson</groupId>
             <artifactId>gson</artifactId>
-            <version>2.9.0</version>
+            <version>2.9.1</version>
             <optional>true</optional>
         </dependency>
         <dependency>

approvaltests-util/pom.xml

@@ -44,7 +44,7 @@
         <dependency>
             <groupId>com.google.code.gson</groupId>
             <artifactId>gson</artifactId>
-            <version>2.9.0</version>
+            <version>2.9.1</version>
             <optional>true</optional>
         </dependency>
         <dependency>

approvaltests/pom.xml

@@ -28,7 +28,7 @@
         <dependency>
             <groupId>com.google.code.gson</groupId>
             <artifactId>gson</artifactId>
-            <version>2.9.0</version>
+            <version>2.9.1</version>
             <scope>compile</scope>
             <optional>true</optional>
         </dependency>