Bump capistrano-rbenv from 2.1.4 to 2.1.6 (#12898)

Bumps [capistrano-rbenv](https://github.com/capistrano/rbenv) from 2.1.4 to 2.1.6.
- [Release notes](https://github.com/capistrano/rbenv/releases)
- [Changelog](https://github.com/capistrano/rbenv/blob/master/CHANGELOG.md)
- [Commits](https://github.com/capistrano/rbenv/compare/v2.1.4...v2.1.6)

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

Gemfile.lock

@@ -80,7 +80,7 @@ GEM
       tzinfo (~> 1.1)
     addressable (2.7.0)
       public_suffix (>= 2.0.2, < 5.0)
-    airbrussh (1.3.4)
+    airbrussh (1.4.0)
       sshkit (>= 1.6.1, != 1.7.0)
     annotate (3.0.3)
       activerecord (>= 3.2, < 7.0)
@@ -139,7 +139,7 @@ GEM
     capistrano-rails (1.4.0)
       capistrano (~> 3.1)
       capistrano-bundler (~> 1.1)
-    capistrano-rbenv (2.1.4)
+    capistrano-rbenv (2.1.6)
       capistrano (~> 3.1)
       sshkit (~> 1.3)
     capistrano-yarn (2.0.2)