This commit adds the list of new and removed metrics to the already existing upgrade guide
from 2025.2 to 2025.3.
Fixes https://github.com/scylladb/scylladb/issues/24697
Closes scylladb/scylladb#25385
(cherry picked from commit f3d9d0c1c7)
Closes scylladb/scylladb#25416