Bump dotenv-rails from 2.7.6 to 2.8.1

Bumps [dotenv-rails](https://github.com/bkeepers/dotenv) from 2.7.6 to 2.8.1.
- [Release notes](https://github.com/bkeepers/dotenv/releases)
- [Changelog](https://github.com/bkeepers/dotenv/blob/master/Changelog.md)
- [Commits](bkeepers/dotenv@v2.7.6...v2.8.1)

---
updated-dependencies:
- dependency-name: dotenv-rails
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -92,9 +92,9 @@ GEM
     diff-lcs (1.5.0)
     digest (3.1.0)
     docile (1.4.0)
-    dotenv (2.7.6)
-    dotenv-rails (2.7.6)
-      dotenv (= 2.7.6)
+    dotenv (2.8.1)
+    dotenv-rails (2.8.1)
+      dotenv (= 2.8.1)
       railties (>= 3.2)
     erubi (1.10.0)
     factory_bot (6.2.0)