CDRIVER-877 delete .mci.yml from libbson
CDRIVER-877 delete .mci.yml from libbson

The libbson test suite is run from libmongoc's .mci.yml in Evergreen
instead.

ajdavis/libbson,Convey-Compliance/libbson,paulmelnikow/libbson,paulmelnikow/libbson,Convey-Compliance/libbson,mongodb/libbson,bjori/libbson,ajdavis/libbson,alexeyvo/libbson,paulmelnikow/libbson,mapr/libbson,mapr/libbson,paulmelnikow/libbson,ajdavis/libbson,rcsanchez97/libbson,bjori/libbson,mongodb/libbson,alexeyvo/libbson,mongodb/libbson,mapr/libbson,Convey-Compliance/libbson,paulmelnikow/libbson,bjori/libbson,alexeyvo/libbson,rcsanchez97/libbson,rcsanchez97/libbson