Remove shebang line

The env-setup script is not intended to be run directly, so it does not
need a shebang line, which might even create the wrong expectations.

Signed-off-by: martin f. krafft <madduck@madduck.net>

hacking/env-setup

-#!/bin/bash
 # usage: source env-setup [-q]
 #        source hacking/env-setup [-q]
 #        . ./env-setup [-q]