tools/magit: replace +magit/clone w/ magit-clone

The former no longer works, since ghub's API has changed. Meanwhile, the
magit-clone command has grown in features to match (and surpass)
+magit/clone, so we'll just use that instead.

modules/tools/magit/config.el

@@ -1,10 +1,5 @@
 ;;; tools/magit/config.el -*- lexical-binding: t; -*-
 
-(defvar +magit-default-clone-url "https://github.com/%s/%s"
-  "The default location for `+magit/clone' to clone relative URLs from.
-It is passed a user and repository name.")
-
-
 ;;
 ;;; Packages