doc/dev: origin of Labeled Perf Counters

Note that Labeled Perf Counters were introduced in Reef.

Fixes: ceph#57753 (comment)

Signed-off-by: Zac Dover <[email protected]>

Author: zdover23

doc/dev/perf_counters.rst

@@ -4,8 +4,6 @@
  Perf counters
 ===============
 
-.. note:: Perf counters were introduced in the Reef release of Ceph.
-
 The perf counters provide generic internal infrastructure for gauges and counters.  The counted values can be both integer and float. There is also an "average" type (normally float) that combines a sum and num counter which can be divided to provide an average.
 
 The intention is that this data will be collected and aggregated by a tool like ``collectd`` or ``statsd`` and fed into a tool like ``graphite`` for graphing and analysis.  Also, note the :doc:`../mgr/prometheus` and the :doc:`../mgr/telemetry`.
@@ -209,6 +207,8 @@ The actual dump is similar to the schema, except that average values are grouped
 Labeled Perf Counters
 ---------------------
 
+.. note:: Labeled perf counters were introduced in the Reef release of Ceph.
+
 A Ceph daemon has the ability to emit a set of perf counter instances with varying labels. These counters are intended for visualizing specific metrics in 3rd party tools like Prometheus and Grafana.
 
 For example, the below counters show the number of put requests for different users on different buckets::