t/lib-gpg.sh: stop pretending to be a stand-alone script

It makes no sense to call `./lib-gpg.sh`. Therefore the hash-bang line
is unnecessary.

There are other similar instances in `t/`, but they are too far from the
context of the enclosing patch series, so they will be addressed
separately.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-gpg.sh

@@ -1,5 +1,3 @@
-#!/bin/sh
-
 gpg_version=$(gpg --version 2>&1)
 if test $? != 127
 then