changed shebang in backup scripts

contrib/backup/config.dist

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # zammad backup script config
 #

contrib/backup/functions

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # zammad backup script functions
 #

contrib/backup/zammad_backup.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # zammad backup script
 #

contrib/backup/zammad_restore.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # zammad restore script
 #