at-spi2-core: upgrade 2.40.1 -> 2.40.2

Upstream release notes:

What's new in at-spi2-core 2.40.2:

* README: Remove outdated links.
* Key grab fixes for the new API.
* registryd: Add a missing call to va_end.

Signed-off-by: Tim Orling <timothy.t.orling@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>