Bump rack from 2.0.7 to 2.2.3

Bumps [rack](https://github.com/rack/rack) from 2.0.7 to 2.2.3.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/master/CHANGELOG.md)
- [Commits](rack/rack@2.0.7...2.2.3)

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

Author: dependabot[bot]

Gemfile.lock

@@ -176,8 +176,7 @@ GEM
     pg (1.1.4)
     popper_js (1.14.5)
     public_suffix (4.0.1)
-    puma (3.12.1)
-    rack (2.0.7)
+    rack (2.2.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails (5.2.3)
@@ -312,7 +311,6 @@ DEPENDENCIES
   nokogiri
   paperclip (~> 6.0.0)
   pg
-  puma (~> 3.11)
   rails (~> 5.2.2)
   remotipart (~> 1.2)
   sass-rails (~> 5.0)