stringify keys of refresh params to match the added id & secret

Author: mrj

lib/omniauth/strategies/oauth2.rb

@@ -105,7 +105,7 @@ def set_access_token_from_hash(hash)
       end
 
       def refresh_access_token
-        self.access_token = access_token&.refresh(token_params.to_hash(symbolize_keys: true), deep_symbolize(options.auth_token_params))
+        self.access_token = access_token&.refresh(token_params.to_hash(stringify_keys: true), deep_symbolize(options.auth_token_params))
       end
 
     protected