test: strengthen API mode redirect_uri assertion to check error= key

Agent-Logs-Url: https://github.com/doorkeeper-gem/doorkeeper/sessions/ba408183-296e-467b-a623-be19597424ae

Co-authored-by: nbulaj <1443426+nbulaj@users.noreply.github.com>

Author: Copilot

spec/controllers/authorizations_controller_spec.rb

@@ -392,7 +392,7 @@ def query_params
       end
 
       it "includes redirect_uri with error info" do
-        expect(response_json_body["redirect_uri"]).to include("unauthorized_client")
+        expect(response_json_body["redirect_uri"]).to include("error=unauthorized_client")
       end
 
       it "does not issue any access token" do