Merge branch 'docs-gitaly-replication-strategy-deprecation' into 'master'

Add election_strategy deprecation notice to the sections header

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/125544



Merged-by: Evan Read <eread@gitlab.com>
Approved-by: Evan Read <eread@gitlab.com>
Reviewed-by: Evan Read <eread@gitlab.com>
Co-authored-by: Kate Grechishkina <khrechyshkina@gitlab.com>