reload: remove .update command

Sopel's not designed to run directly from a Git working directory any
more, so let's not advertise this command that relies upon it.

sopel/modules/reload.py

@@ -56,19 +56,6 @@ def f_reload(bot, trigger):
     ))
 
 
-@plugin.nickname_command('update')
-@plugin.require_admin
-@plugin.output_prefix(PLUGIN_OUTPUT_PREFIX)
-def f_update(bot, trigger):
-    """Pulls the latest versions of all plugins from Git (for use by admins only)."""
-    proc = subprocess.Popen('/usr/bin/git pull',
-                            stdout=subprocess.PIPE,
-                            stderr=subprocess.PIPE, shell=True)
-    bot.reply(proc.communicate()[0])
-
-    f_reload(bot, trigger)
-
-
 @plugin.nickname_command("load")
 @plugin.priority("low")
 @plugin.thread(False)