Bump dotenv from 2.7.6 to 2.8.1

Bumps [dotenv](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
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -20,7 +20,7 @@ GEM
       multi_json
     domain_name (0.5.20190701)
       unf (>= 0.0.5, < 1.0.0)
-    dotenv (2.7.6)
+    dotenv (2.8.1)
     excon (0.92.3)
     fpm (1.14.2)
       arr-pm (~> 0.0.11)