Restore GitRefValidator per CE

EE contained various cosmetic changes that behave the same way as in CE,
they just look different. This restores the file per CE, ensuring both
CE and EE use the same code.

lib/gitlab/git_ref_validator.rb

@@ -6,15 +6,14 @@ module Gitlab
   module GitRefValidator
     extend self
 
-    EXPANDED_PREFIXES = %w(refs/heads/ refs/remotes/).freeze
-    DISALLOWED_PREFIXES = %w(-).freeze
+    EXPANDED_PREFIXES = %w[refs/heads/ refs/remotes/].freeze
+    DISALLOWED_PREFIXES = %w[-].freeze
 
     # Validates a given name against the git reference specification
     #
     # Returns true for a valid reference name, false otherwise
     def validate(ref_name)
-      return false if ref_name.start_with?(*EXPANDED_PREFIXES)
-      return false if ref_name.start_with?(*DISALLOWED_PREFIXES)
+      return false if ref_name.start_with?(*(EXPANDED_PREFIXES + DISALLOWED_PREFIXES))
       return false if ref_name == 'HEAD'
 
       begin