Bump dotenv-rails from 2.8.1 to 3.1.2 (#750)

Bumps [dotenv-rails](https://github.com/bkeepers/dotenv) from 2.8.1 to 3.1.2.
- [Release notes](https://github.com/bkeepers/dotenv/releases)
- [Changelog](https://github.com/bkeepers/dotenv/blob/main/Changelog.md)
- [Commits](bkeepers/dotenv@v2.8.1...v3.1.2)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -146,10 +146,10 @@ GEM
       thread_safe (~> 0.3, >= 0.3.1)
     diff-lcs (1.5.1)
     docile (1.4.0)
-    dotenv (2.8.1)
-    dotenv-rails (2.8.1)
-      dotenv (= 2.8.1)
-      railties (>= 3.2)
+    dotenv (3.1.2)
+    dotenv-rails (3.1.2)
+      dotenv (= 3.1.2)
+      railties (>= 6.1)
     drb (2.2.1)
     erubi (1.12.0)
     execjs (2.9.1)