sysadm: Fix remaining warning on sysadm docs
- sysadm: Rename reference to the correct one (mirror_graph_replayer)
- sysadm/mirror-operations: Fix nonexisting document warning
- sysadm: Fix toctree contains reference to nonexisting document
Related to #3648 (closed)
Test Plan
make -C sysadm clean html
until it stops complaining.
Migrated from D6464 (view on Phabricator)