Bump bootstrap_form from 4.3.0 to 4.4.0

Bumps [bootstrap_form](https://github.com/bootstrap-ruby/bootstrap_form) from 4.3.0 to 4.4.0.
- [Release notes](https://github.com/bootstrap-ruby/bootstrap_form/releases)
- [Changelog](https://github.com/bootstrap-ruby/bootstrap_form/blob/master/CHANGELOG.md)
- [Commits](bootstrap-ruby/bootstrap_form@v4.3.0...v4.4.0)

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

Gemfile.lock

@@ -57,7 +57,7 @@ GEM
     bootstrap-sass (3.4.1)
       autoprefixer-rails (>= 5.2.1)
       sassc (>= 2.0.0)
-    bootstrap_form (4.3.0)
+    bootstrap_form (4.4.0)
       actionpack (>= 5.0)
       activemodel (>= 5.0)
     builder (3.2.4)
@@ -216,7 +216,7 @@ GEM
     parser (2.7.0.3)
       ast (~> 2.4.0)
     public_suffix (4.0.3)
-    rack (2.1.2)
+    rack (2.2.2)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails (5.2.4.1)