Fix formatting issue

Author: 8sd

doc/self-hosted/index.md

@@ -43,7 +43,7 @@ Options:
   --cert <value>
   --cert-key <value>
   -e, --extensions-dir <dir>  Set the root path for extensions.
-  -d --user-data-dir <dir>    Specifies the directory that user data is kept in, useful when running as root.
+  -d, --user-data-dir <dir>    Specifies the directory that user data is kept in, useful when running as root.
   --data-dir <value>          DEPRECATED: Use '--user-data-dir' instead. Customize where user-data is stored.
   -h, --host <value>          Customize the hostname. (default: "0.0.0.0")
   -o, --open                  Open in the browser on startup.