Bump rollbar from 3.4.2 to 3.5.1

Bumps [rollbar](https://github.com/rollbar/rollbar-gem) from 3.4.2 to 3.5.1.
- [Release notes](https://github.com/rollbar/rollbar-gem/releases)
- [Changelog](https://github.com/rollbar/rollbar-gem/blob/master/CHANGELOG.md)
- [Commits](rollbar/rollbar-gem@v3.4.2...v3.5.1)

---
updated-dependencies:
- dependency-name: rollbar
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -381,7 +381,7 @@ GEM
       actionpack (>= 5.2)
       railties (>= 5.2)
     rexml (3.2.6)
-    rollbar (3.4.2)
+    rollbar (3.5.1)
     rollout (2.5.0)
       redis (~> 4.0)
     rollout-ui (0.5.3)