Bump rack from 1.6.13 to 2.2.3

Bumps [rack](https://github.com/rack/rack) from 1.6.13 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@1.6.13...2.2.3)

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

Gemfile.lock

@@ -8,8 +8,8 @@ GEM
   specs:
     diff-lcs (1.4.4)
     hashie (4.1.0)
-    oa-core (0.0.5)
-      rack (~> 1.1)
+    oa-core (0.0.3)
+      rack
     oa-openid (0.0.2)
       oa-core (~> 0.0.0)
       rack-openid
@@ -20,7 +20,7 @@ GEM
     omniauth-openid (2.0.1)
       omniauth (>= 1.0, < 3.0)
       rack-openid (~> 1.4.0)
-    rack (1.6.13)
+    rack (2.2.3)
     rack-openid (1.4.2)
       rack (>= 1.1.0)
       ruby-openid (>= 2.1.8)
@@ -45,6 +45,7 @@ GEM
       ruby-openid (>= 2.1.7)
 
 PLATFORMS
+  ruby
   x86_64-linux
 
 DEPENDENCIES