Bump dockerfile-rails from 1.6.13 to 1.6.14

Bumps [dockerfile-rails](https://github.com/fly-apps/dockerfile-rails) from 1.6.13 to 1.6.14.
- [Release notes](https://github.com/fly-apps/dockerfile-rails/releases)
- [Commits](fly-apps/dockerfile-rails@v1.6.13...v1.6.14)

---
updated-dependencies:
- dependency-name: dockerfile-rails
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -186,7 +186,7 @@ GEM
       thread_safe (~> 0.3, >= 0.3.1)
     diff-lcs (1.5.1)
     docile (1.4.0)
-    dockerfile-rails (1.6.13)
+    dockerfile-rails (1.6.14)
       rails (>= 3.0.0)
     dotenv (3.1.2)
     dotenv-rails (3.1.2)