Juju status incorrectly notes the number of units for OSDs

[Ponnuvel Palaniyappan]

Here's a simple bundle:
```
series: focal
applications:
  ceph-mon:
    charm: ceph-mon
    channel: pacific/stable
    revision: 113
    num_units: 1
    to:
    - "0"
    options:
      expected-osd-count: 3
      loglevel: 1
      monitor-count: 1
      monitor-secret: AQCXrnZQwI7KGBAAiPofmKEXKxu5bUzoYLVkbQ==
      source: cloud:focal-xena
    constraints: arch=amd64 mem=2048
  ceph-osd:
    charm: ceph-osd
    channel: pacific/stable
    revision: 537
    num_units: 3
    to:
    - "1"
    - "2"
    - "3"
    options:
      loglevel: 1
      osd-devices: ""
      source: cloud:focal-xena
    constraints: arch=amd64 mem=1024
    storage:
      bluestore-db: loop,0,1024
      bluestore-wal: loop,0,1024
      osd-devices: cinder,1,10240
      osd-journals: loop,0,1024
machines:
  "0":
    constraints: arch=amd64 mem=2048
  "1":
    constraints: arch=amd64 mem=1024
  "2":
    constraints: arch=amd64 mem=1024
  "3":
    constraints: arch=amd64 mem=1024
relations:
- - ceph-mon:osd
  - ceph-osd:mon
```

When deployed, `juju status` reports incorrect number of OSDs in the App section:
```
Model Controller Cloud/Region Version SLA Timestamp
pacific con282 stsstack/stsstack 2.9.31 unsupported 16:33:33Z

App Version Status Scale Charm Channel Rev Exposed Message
ceph-mon 16.2.9 active 1 ceph-mon pacific/stable 113 no Unit is ready and clustered
ceph-osd 16.2.9 active 3 ceph-osd pacific/stable 537 no Unit is ready (1 OSD)

Unit Workload Agent Machine Public address Ports Message
ceph-mon/0* active idle 0 10.5.4.21 Unit is ready and clustered
ceph-osd/0* active idle 1 10.5.1.228 Unit is ready (1 OSD)
ceph-osd/1 active idle 2 10.5.2.143 Unit is ready (1 OSD)
ceph-osd/2 active idle 3 10.5.3.0 Unit is ready (1 OSD)

Machine State Address Inst id Series AZ Message
0 started 10.5.4.21 43f50f78-3dd5-4faa-9aab-ce1807602711 focal nova ACTIVE
1 started 10.5.1.228 89f6120b-a06e-42eb-a9a2-ee3ed3fbc0b6 focal nova ACTIVE
2 started 10.5.2.143 98623721-73ae-4c8a-9afa-9742c5647525 focal nova ACTIVE
3 started 10.5.3.0 be456861-dae1-41e9-9cbe-336b126c3730 focal nova ACTIVE
```

i.e. there are 3 OSDs but it reports:
```
ceph-osd 16.2.9 active 3 ceph-osd pacific/stable 537 no Unit is ready (1 OSD)
```

The individual units report correctly. I think the message simply needs to drop the "(<num> OSD)" part from the App section.