Git.pm: remove redundant "use strict" from sub-package

In Perl the "use strict/warnings" pragmas are lexical, thus there's no reason to do: package Foo; use strict; package Bar; use strict; $x = 5; To satisfy the desire that the undeclared $x variable will be spotted at compile-time. It's enough to include the first "use strict". This functionally changes nothing, but makes a subsequent change where "use warnings" will be added to Git.pm less confusing and less verbose, since as with "strict" we'll only need to do that at the top of the file. Changes code initially added in a6065b548f ("Git.pm: Try to support ActiveState output pipe", 2006-06-25). Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>