[glossary] Fix acronym: BMC
[glossary] Fix acronym: BMC

- Fix entry for BMC (Baseband Management Controller)

Change-Id: Idc33e9018fe4f4aafe877edbc4d5802b3fa7ae8a
Implements: blueprint improve-glossary-usage

openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals