make some shebangs comply to posix standard

advanced/Scripts/wildcard_regex_converter.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # Pi-hole: A black hole for Internet advertisements
 # (c) 2017 Pi-hole, LLC (https://pi-hole.net)
 # Network-wide ad blocking via your own hardware.

advanced/Templates/pihole-FTL.service

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 ### BEGIN INIT INFO
 # Provides:          pihole-FTL
 # Required-Start:    $remote_fs $syslog

pihole

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # Pi-hole: A black hole for Internet advertisements
 # (c) 2017 Pi-hole, LLC (https://pi-hole.net)