Bump dotenv-rails from 2.7.6 to 2.8.1 (#18898)

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](https://github.com/bkeepers/dotenv/compare/v2.7.6...v2.8.1)

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

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

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

Gemfile

@@ -16,7 +16,7 @@ gem 'hamlit-rails', '~> 0.2'
 gem 'pg', '~> 1.4'
 gem 'makara', '~> 0.5'
 gem 'pghero', '~> 2.8'
-gem 'dotenv-rails', '~> 2.7'
+gem 'dotenv-rails', '~> 2.8'
 
 gem 'aws-sdk-s3', '~> 1.114', require: false
 gem 'fog-core', '<= 2.1.0'