aliases/apt: use `_command_exists`

aliases/available/apt.aliases.bash

@@ -1,4 +1,4 @@
-#!/bin/bash
+# shellcheck shell=bash
 #
 # -binaryanomaly
 
@@ -8,7 +8,8 @@ about-alias 'Apt and dpkg aliases for Ubuntu and Debian distros.'
 # set apt aliases
 function _set_pkg_aliases()
 {
-	if [ -x $(which apt) ]; then
+	if _command_exists apt
+	then
 		alias apts='apt-cache search'
 		alias aptshow='apt-cache show'
 		alias aptinst='sudo apt-get install -V'