contrib: use a more portable shebang for git-credential-netrc

While the installed scripts have their Perl shebang set to PERL_PATH,
it is nevertheless useful to be able to run the uninstalled script for
manual tests while developing. This change makes the shebang more
portable by having the perl command looked from PATH instead of from a
fixed location.

Signed-off-by: Maxim Cournoyer <maxim@guixotic.coop>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/credential/netrc/git-credential-netrc.perl

@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 use strict;
 use warnings;