ca-certificates: remove

This is now in OE-Core as of ad2851cf0abc2ab35e0f60c96d3142c29a07c8fc.
ca-certificates-cross is no longer used (effectively replaced by a native
BBCLASSEXTEND in the main recipe).

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>