Remove deprecated .github/stale.yml to address #837 (#838)

SUMMARY
I noticed that even config for probot/stale is present in the repo, but the old issues and PRs weren't marked as stale and not closed by the bot. Investigated and found that this bot was added to community.kubernetes as ansible-collections/community.kubernetes#53 but wasn't moved to kubernetes.core and never worked here.
Moreover, this bot is completely deprecated and down, ref: probot/stale#430
So, the config to be removed.
ISSUE TYPE

Bugfix Pull Request

COMPONENT NAME
.github/stale.yml
ADDITIONAL INFORMATION
Closes #837
Trivial change that not require changelog

Reviewed-by: Mike Graves <mgraves@redhat.com>