docs(gas): update plugin url (#11918)

plugins/gas/README.md

@@ -1,6 +1,6 @@
 # Gas plugin
 
-This plugin adds autocompletion for the [gas](http://walle.github.com/gas) command,
+This plugin adds autocompletion for the [gas](http://ramblingsby.me/gas/) command,
 a utility to manage Git authors.
 
 To use it, add `gas` to the plugins array of your zshrc file: