build: Remove default values from descriptions in meson_options.txt
build: Remove default values from descriptions in meson_options.txt

People should be able to get these from meson itself, or by reading
`meson_options.txt`. Putting them in the description strings is just
going to lead to that going out of sync with the actual options.

Spotted by Debarshi Ray in !23.

Signed-off-by: Philip Withnall <29c2a2ac2a854b9cf047275aa9de346d096be2e0@endlessm.com>

GNOME/libgdata