[Infra] Bump Auth sample app's dep. on RecaptchaEnterprise (#14418)

Author: ncooke3

FirebaseAuth/Tests/SampleSwift/Podfile

@@ -15,7 +15,7 @@ target 'AuthenticationExample' do
  pod 'FirebaseAuthInterop', :path => '../../..'
  pod 'FirebaseAppCheckInterop', :path => '../../..'
 
- pod 'RecaptchaEnterprise', '~> 18.3'
+ pod 'RecaptchaEnterprise', '~> 18.7'
 
  ## Pod for Sign in with Google
  pod 'GoogleSignIn'