Increase gem 'config' version

The current gem `config` version (1.7.2, Gemfile.lock) is not compatible
with Ruby 2.7 due to a protected method that has been removed from Ruby
OpenStruct class (standard library).

To correctly suppport Ruby 2.7 within rmt-server, I increased the gem
version to the latest release (2.2.1) which fixes the described issue.

Links:

* Issue: rubyconfig/config#259
* Pull Request: rubyconfig/config#255
* Release: https://github.com/rubyconfig/config/releases/tag/2.2.1

Gemfile

@@ -84,7 +84,7 @@ gem 'active_model_serializers'
 gem 'fast_gettext'
 gem 'gettext_i18n_rails'
 
-gem 'config', '~> 1.0'
+gem 'config', '~> 2.2', '>= 2.2.1'
 gem 'terminal-table', '~> 1.8'
 
 # needed by rmt-server-pubcloud

Gemfile.lock

@@ -47,10 +47,9 @@ GEM
     coderay (1.1.2)
     colored2 (3.1.2)
     concurrent-ruby (1.1.6)
-    config (1.7.2)
-      activesupport (>= 3.0)
+    config (2.2.1)
       deep_merge (~> 1.2, >= 1.2.1)
-      dry-validation (~> 0.12, >= 0.12.2, < 1.0.0)
+      dry-validation (~> 1.0, >= 1.0.0)
     cork (0.3.0)
       colored2 (~> 3.1)
     coveralls (0.8.23)
@@ -81,34 +80,44 @@ GEM
     deep_merge (1.2.1)
     diff-lcs (1.3)
     docile (1.3.1)
-    dry-configurable (0.8.3)
+    dry-configurable (0.11.5)
       concurrent-ruby (~> 1.0)
       dry-core (~> 0.4, >= 0.4.7)
-    dry-container (0.7.1)
+      dry-equalizer (~> 0.2)
+    dry-container (0.7.2)
       concurrent-ruby (~> 1.0)
       dry-configurable (~> 0.1, >= 0.1.3)
-    dry-core (0.4.7)
+    dry-core (0.4.9)
       concurrent-ruby (~> 1.0)
-    dry-equalizer (0.2.2)
-    dry-inflector (0.1.2)
-    dry-logic (0.6.1)
+    dry-equalizer (0.3.0)
+    dry-inflector (0.2.0)
+    dry-initializer (3.0.3)
+    dry-logic (1.0.6)
       concurrent-ruby (~> 1.0)
       dry-core (~> 0.2)
       dry-equalizer (~> 0.2)
-    dry-types (0.14.1)
+    dry-schema (1.5.1)
+      concurrent-ruby (~> 1.0)
+      dry-configurable (~> 0.8, >= 0.8.3)
+      dry-core (~> 0.4)
+      dry-equalizer (~> 0.2)
+      dry-initializer (~> 3.0)
+      dry-logic (~> 1.0)
+      dry-types (~> 1.4)
+    dry-types (1.4.0)
       concurrent-ruby (~> 1.0)
       dry-container (~> 0.3)
       dry-core (~> 0.4, >= 0.4.4)
-      dry-equalizer (~> 0.2)
+      dry-equalizer (~> 0.3)
       dry-inflector (~> 0.1, >= 0.1.2)
-      dry-logic (~> 0.5, >= 0.5)
-    dry-validation (0.13.3)
+      dry-logic (~> 1.0, >= 1.0.2)
+    dry-validation (1.5.0)
       concurrent-ruby (~> 1.0)
-      dry-configurable (~> 0.1, >= 0.1.3)
-      dry-core (~> 0.2, >= 0.2.1)
+      dry-container (~> 0.7, >= 0.7.1)
+      dry-core (~> 0.4)
       dry-equalizer (~> 0.2)
-      dry-logic (~> 0.5, >= 0.5.0)
-      dry-types (~> 0.14.0)
+      dry-initializer (~> 3.0)
+      dry-schema (~> 1.5)
     erubi (1.8.0)
     ethon (0.11.0)
       ffi (>= 1.3.0)
@@ -331,7 +340,7 @@ DEPENDENCIES
   activesupport (~> 5.1.3)
   awesome_print
   byebug
-  config (~> 1.0)
+  config (~> 2.2, >= 2.2.1)
   coveralls (~> 0.8.21)
   danger
   danger-rubocop