Bump doorkeeper from 5.2.0 to 5.2.1 (#11934)

Bumps [doorkeeper](https://github.com/doorkeeper-gem/doorkeeper) from 5.2.0 to 5.2.1.
- [Release notes](https://github.com/doorkeeper-gem/doorkeeper/releases)
- [Changelog](https://github.com/doorkeeper-gem/doorkeeper/blob/master/CHANGELOG.md)
- [Commits](https://github.com/doorkeeper-gem/doorkeeper/compare/v5.2.0...v5.2.1)

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

Gemfile.lock

@@ -209,7 +209,7 @@ GEM
     docile (1.3.2)
     domain_name (0.5.20180417)
       unf (>= 0.0.5, < 1.0.0)
-    doorkeeper (5.2.0)
+    doorkeeper (5.2.1)
       railties (>= 5)
     dotenv (2.7.5)
     dotenv-rails (2.7.5)