message: core-app-api: fix isReactRouterBeta test
diff: describe.each(['beta', 'stable'])('react-router %s', rrVersion => {
  it('should return the correct value for the different version', () => {
  jest.isolateModules(() => {
  + jest.doMock('react-router', () =>
  + rrVersion === 'beta'
  + ? jest.requireActual('react-router-beta')
  + : jest.requireActual('react-router-stable'),
  + );
  jest.doMock('react-router-dom', () =>
  rrVersion === 'beta'
  ? jest.requireActual('react-router-dom-beta')
  