Bump doorkeeper from 4.3.0 to 4.3.1

Bumps [doorkeeper](https://github.com/doorkeeper-gem/doorkeeper) from 4.3.0 to 4.3.1.
- [Release notes](https://github.com/doorkeeper-gem/doorkeeper/releases)
- [Changelog](https://github.com/doorkeeper-gem/doorkeeper/blob/master/NEWS.md)
- [Commits](doorkeeper-gem/doorkeeper@v4.3.0...v4.3.1)

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

Gemfile.lock

@@ -97,13 +97,13 @@ GEM
     docile (1.1.5)
     domain_name (0.5.20170404)
       unf (>= 0.0.5, < 1.0.0)
-    doorkeeper (4.3.0)
+    doorkeeper (4.3.1)
       railties (>= 4.2)
     dotenv (2.2.1)
     dotenv-rails (2.2.1)
       dotenv (= 2.2.1)
       railties (>= 3.2, < 5.2)
-    erubi (1.7.0)
+    erubi (1.7.1)
     exception_notification (4.2.2)
       actionmailer (>= 4.0, < 6)
       activesupport (>= 4.0, < 6)