doc/src/common/options: mgr.yaml.in edit

Improve the "desc" field under the "mgr_data" entry in
src/common/options/mgr.yaml.in.

This is a test to determine whether the Jenkins tests can be passed.
This test is made after the mystifying failure of
ceph#62983.

Signed-off-by: Zac Dover <[email protected]>
(cherry picked from commit 30411f3)

Author: zdover23

src/common/options/mgr.yaml.in

@@ -5,7 +5,8 @@ options:
 - name: mgr_data
   type: str
   level: advanced
-  desc: Filesystem path to the ceph-mgr data directory, used to contain keyring.
+  desc: Filesystem path to the Manager's data directory, which contains
+    keyrings and other data 
   fmt_desc: Path to load daemon data (such as keyring)
   default: /var/lib/ceph/mgr/$cluster-$id
   services: