maintcheck: avoid yet more spurious failures (1)

maintcheck: avoid yet more spurious failures (1)

The 'sc_tests_makefile_variable_order' maintainer check is too
strict sometimes, blaming automake for outputting out-of-order
variables when this is in fact due to the result of post-processing
of third-party tools or custom test code.

* t/tap-doc2.sh: Ensure the final Makefile.in (that we hack by
hand) is removed, to avoid a spurious maintainer-check failure.
* t/gettext-macros.sh: Ensure that any leftover Makefile.in (that
is generated by gettext/autopoint) is removed, to avoid a spurious
maintainer-check failure.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>