perl/Git.pm: typofix in a comment

No change of behaviour intended.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

perl/Git.pm

@@ -531,7 +531,7 @@ If TIME is not supplied, the current local time is used.
 =cut
 
 sub get_tz_offset {
-	# some systmes don't handle or mishandle %z, so be creative.
+	# some systems don't handle or mishandle %z, so be creative.
 	my $t = shift || time;
 	my $gm = timegm(localtime($t));
 	my $sign = qw( + + - )[ $gm <=> $t ];