Rename LFS_JWT_SECRET to include OAUTH2 as well (#6826)

doc/usage/command-line.en-us.md

@@ -161,11 +161,11 @@ for automatic deployments.
     - `secret`:
         - Options:
             - `INTERNAL_TOKEN`: Token used for an internal API call authentication.
-            - `LFS_JWT_SECRET`: LFS authentication secret.
+            - `JWT_SECRET`: LFS & OAUTH2 JWT authentication secret (LFS_JWT_SECRET is aliased to this option for backwards compatibility).
             - `SECRET_KEY`: Global secret key.
         - Examples:
             - `gitea generate secret INTERNAL_TOKEN`
-            - `gitea generate secret LFS_JWT_SECRET`
+            - `gitea generate secret JWT_SECRET`
             - `gitea generate secret SECRET_KEY`
 
 #### keys