fix: instruct people to restart their terminals

modifying shell rc files don't have immediate effect and it's confusing
if you don't know this.

docs/abra/cheat-sheet.md

@@ -15,6 +15,8 @@ Definitely set up autocomplete or you'll be sad :sob: `abra` supports `bash`,
 
 ```
 $ abra autocomplete bash
+# Restart your terminal or load autocompletion in place
+$ source /etc/bash_completion.d/abra
 ```