Update README.md to indicate skip_ssrf_protection should be used only…

… when necessary

Co-authored-by: Yohta Kimura <38206553+rajyan@users.noreply.github.com>

README.md

@@ -659,7 +659,11 @@ end
 ## Testing with CarrierWave
 
 It's a good idea to test your uploaders in isolation. In order to speed up your
-tests, it's recommended to switch off processing in your tests, disable SSRF protection, and to use the
+tests, it's recommended to switch off processing in your tests, and to use the file storage.
+Also, you can disable SSRF protection at your own risk using the `skip_ssrf_protection` configuration.
+
+In Rails you could do that by adding an initializer with:
+
 file storage. In Rails you could do that by adding an initializer with:
 
 ```ruby