man: clean up weston.ini mark-up

Try to reduce the cargo-culted directives that do not seem to have any
effect on the output.

I verified that are no changes by doing before this patch

	$ man -Tpdf man/weston.ini.5 > ref.pdf

and then after this patch

	$ ninja && man -Tpdf man/weston.ini.5 > test.pdf

and looking at

	$ diffpdf ref.pdf test.pdf

I used PDF as the format for comparisons, because it can express much
more typesetting features than plain text.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>