fix(docopt): whitespace typo in `--help` output

Fix a whitespace (alignment) typo in the `--help` output.

cmd/cheat/docopt.txt

@@ -56,4 +56,4 @@ Examples:
     cheat --rm foo/bar
 
   To view the configuration file path:
-	cheat --conf
+    cheat --conf

cmd/cheat/str_usage.go

@@ -65,6 +65,6 @@ Examples:
     cheat --rm foo/bar
 
   To view the configuration file path:
-	cheat --conf
+    cheat --conf
 `)
 }