Revert "Symbolize client_auth_method for quirked providers"

This reverts commit 83a870bf.
Signed-off-by: Vincent Fazio <vfazio@xes-inc.com>

lib/gitlab/omniauth_initializer.rb

@@ -96,16 +96,6 @@ module Gitlab
         args[:strategy_class] = args[:strategy_class].constantize
       end
 
-      # Providers that are known to depend on rack-oauth2, like those using
-      # Omniauth::Strategies::OpenIDConnect, need to be quirked so the
-      # client_auth_method argument value is passed as a symbol.
-      if (args[:strategy_class] == OmniAuth::Strategies::OpenIDConnect ||
-        args[:name] == 'openid_connect') &&
-        args[:client_auth_method].is_a?(String)
-
-        args[:client_auth_method] = args[:client_auth_method].to_sym
-      end
-
       args
     end