note dependency on ENABLE_CAPTCHA

Author: AJ ONeal

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -215,7 +215,7 @@ Values containing `#` or `;` must be quoted using `` ` `` or `"""`.
    provided email rather than a generated email.
 - `ENABLE_CAPTCHA`: **false**: Enable this to use captcha validation for registration.
 - `REQUIRE_EXTERNAL_REGISTRATION_CAPTCHA`: **false**: Enable this to force captcha validation
-   even for External Accounts (i.e. GitHub, OpenID Connect, etc).
+   even for External Accounts (i.e. GitHub, OpenID Connect, etc). You must `ENABLE_CAPTCHA` also.
 - `CAPTCHA_TYPE`: **image**: \[image, recaptcha\]
 - `RECAPTCHA_SECRET`: **""**: Go to https://www.google.com/recaptcha/admin to get a secret for recaptcha.
 - `RECAPTCHA_SITEKEY`: **""**: Go to https://www.google.com/recaptcha/admin to get a sitekey for recaptcha.
@@ -401,7 +401,7 @@ NB: You must `REDIRECT_MACARON_LOG` and have `DISABLE_ROUTER_LOG` set to `false`
 
 ## Metrics (`metrics`)
 
-- `ENABLED`: **false**: Enables /metrics endpoint for prometheus. 
+- `ENABLED`: **false**: Enables /metrics endpoint for prometheus.
 - `TOKEN`: **\<empty\>**: You need to specify the token, if you want to include in the authorization the metrics . The same token need to be used in prometheus parameters `bearer_token` or `bearer_token_file`.
 
 ## API (`api`)