doc/rados: repair short underline

Repair a too-short underline that was introduced in
ceph@babd3c0.

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

Author: zdover23

doc/rados/configuration/mon-config-ref.rst

@@ -630,7 +630,7 @@ Miscellaneous
 .. confval:: enable_availability_tracking
 
 NVMe-oF Monitor Client
-=====================
+======================
 
 .. confval:: nvmeof_mon_client_disconnect_panic
 .. confval:: nvmeof_mon_client_connect_panic