improve upgrade instructions

FAQ.md

@@ -53,10 +53,15 @@ There are roughly 3 kinds of packages:
 > :warning: Remember to backup your dotfiles and other sensitive data first.
 
 ```
-rm -rf "$fish_path"
 curl -L git.io/omf | sh
 ```
 
+You can now safely remove `$fish_path`.
+
+```fish
+rm -rf "$fish_path"
+```
+
 
 ## I changed my prompt with `fish_config` and now I can't get my Oh My Fish theme's prompt back, what do I do?