gettext API users: don't explicitly cast ngettext()'s "n"

gettext API users: don't explicitly cast ngettext()'s "n"

Change a few stray users of the inline gettext.h Q_() function to stop
casting its "n" argument, the vast majority of the users of that
wrapper API use the implicit cast to "unsigned long".

The ngettext() function (which Q_() resolves to) takes an "unsigned
long int", and so does our Q_() wrapper for it, see 0c9ea33b90f (i18n:
add stub Q_() wrapper for ngettext, 2011-03-09). The function isn't
ours, but provided by e.g. GNU libintl.

This amends code added in added in 7171a0b0cf5 (index-pack: correct
"len" type in unpack_data(), 2016-07-13). The cast it added for the
printf format to die() was needed, but not the cast to Q_().

Likewise the casts in strbuf.c added in 8f354a1faed (l10n: localizable
upload progress messages, 2019-07-02) and for
builtin/merge-recursive.c in ccf7813139f (i18n: merge-recursive: mark
error messages for translation, 2016-09-15) weren't needed.

In the latter case the cast was copy/pasted from the argument to
warning() itself, added in b74d779bd90 (MinGW: Fix compiler warning in
merge-recursive, 2009-05-23). The cast for warning() is needed, but
not the one for ngettext()'s "n" argument.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>