These features must not depend on TIFF_FOUND/WrapWebP_FOUND, otherwise
it's impossible to use the bundled libtiff/libwebp.
The default-converted conditions are good enough.
This reverts 82941a3f1b which tried to fix
the qtimageformats build. More work to fix the bundled libwebp is to be
done in the qtimageformats repo.
Change-Id: I5050a6e5f2b3c95e3d5fea660f7fbb630113b7dd
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>