Bump vcr from 6.2.0 to 6.3.1 in /backend

Bumps [vcr](https://github.com/vcr/vcr) from 6.2.0 to 6.3.1.
- [Release notes](https://github.com/vcr/vcr/releases)
- [Changelog](https://github.com/vcr/vcr/blob/master/CHANGELOG.md)
- [Commits](vcr/vcr@v6.2.0...v6.3.1)

---
updated-dependencies:
- dependency-name: vcr
  dependency-version: 6.3.1
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

backend/Gemfile.lock

@@ -494,7 +494,8 @@ GEM
       concurrent-ruby (~> 1.0)
     unicode-display_width (2.5.0)
     uniform_notifier (1.16.0)
-    vcr (6.2.0)
+    vcr (6.3.1)
+      base64
     warden (1.2.9)
       rack (>= 2.0.9)
     webmock (3.26.1)