Remove amd64-debian-11-msan and last-N-failed from status reporting

As per cvicentiu request

debian-11-msan It will be replaced by a clang-20 builder in https://github.com/MariaDB/buildbot/pull/562 (cc: danblack )
is not a protected branches builder, only reporting its status to GitHub and is causing unnecessary failures.
I will not create a separate Pull Request for it as its replacement is handled in MDBF-793 as mentioned,

last-N-failed is also only reporting its status and cvicentiu reported often sporadic failures for it.

I will remove them from GITHUB_STATUS_BUILDERS in buildbot.mariadb.org
and restart master-docker-nonstandard-2 / master-protected-branches to pick-up the changes.