Bump gson from 2.9.0 to 2.9.1 in /fhir-parent

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:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

fhir-parent/pom.xml

@@ -234,7 +234,7 @@
             <dependency>
                 <groupId>com.google.code.gson</groupId>
                 <artifactId>gson</artifactId>
-                <version>2.9.0</version>
+                <version>2.9.1</version>
             </dependency>
             <dependency>
                 <groupId>org.apache.derby</groupId>