build(deps): bump com.google.guava:guava from 1.55.0 to 23.0 in /backend

Bumps [com.google.guava:guava](https://github.com/google/guava) from 1.55.0 to 23.0.
- [Release notes](https://github.com/google/guava/releases)
- [Commits](https://github.com/google/guava/commits/v23.0)

---
updated-dependencies:
- dependency-name: com.google.guava:guava
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

backend/build.gradle

@@ -54,7 +54,7 @@ dependencies {
 
   // Fleet Engine Auth Library and its dependencies
   implementation 'com.google.maps:fleetengine-auth:1.8.0'
-  implementation 'com.google.guava:guava:1.55.0'
+  implementation 'com.google.guava:guava:23.0'
   implementation 'com.google.auth:google-auth-library-oauth2-http:0.26.0'
 
   implementation 'com.auth0:java-jwt:3.10.2'