upgrade 14/stable from r429 to r553 fails with PostgreSQLEnableDisableExtensionError

## Steps to reproduce

1. deploy postgresql r429 from 14/stable in ubuntu@22.04 machine model
2. relate an application to it and use it (e.g. netbox)
3. upgrade postgresql to r553 from 14/stable

## Expected behavior

Upgrade succeeds.

## Actual behavior

Upgrade fails.

```
stg-netbox@is-bastion-ps6:~$ juju status postgresql
Model Controller Cloud/Region Version SLA Timestamp
stg-netbox juju-controller-34-staging-ps6 prodstack6/prodstack6 3.4.5 unsupported 02:07:40Z

App Version Status Scale Charm Channel Rev Exposed Message
postgresql 14.11 active 3 postgresql 14/stable 553 no

Unit Workload Agent Machine Public address Ports Message
postgresql/9 waiting idle 34 10.142.102.31 5432/tcp awaiting for member to start
postgresql/10 waiting idle 32 10.142.102.240 5432/tcp awaiting for member to start
postgresql/11* error idle 33 10.142.102.89 5432/tcp hook failed: "database-relation-changed"

Machine State Address Inst id Base AZ Message
32 started 10.142.102.240 244ca796-afb2-4f0d-864a-0204e17c17f7 ubuntu@22.04 availability-zone-3 ACTIVE
33 started 10.142.102.89 2696446e-eb3b-4fa2-9e59-d9b453a30b85 ubuntu@22.04 availability-zone-3 ACTIVE
34 started 10.142.102.31 b05d1ccb-fd1e-45ee-adea-56c0956a6011 ubuntu@22.04 availability-zone-1 ACTIVE

Offer Application Charm Rev Connected Endpoint Interface Role
postgresql postgresql postgresql 553 1/1 database postgresql_client provider
```

## Versions

Operating system: Ubuntu 22.04.4 LTS

Juju CLI: 3.4.6-ubuntu-amd64

Juju agent: 3.4.5

Charm revision: 553

LXD: n/a

## Log output

Juju debug log: see snippet below

```
unit-postgresql-11: 2025-03-21 01:26:36 INFO juju.worker.uniter unit "postgresql/11" started
unit-postgresql-11: 2025-03-21 01:26:36 INFO juju.worker.uniter hooks are retried true
unit-postgresql-11: 2025-03-21 01:26:37 INFO juju.worker.uniter.charm downloading ch:amd64/jammy/postgresql-553 from API server
unit-postgresql-11: 2025-03-21 01:27:39 INFO juju.worker.uniter found queued "upgrade-charm" hook
unit-postgresql-11: 2025-03-21 01:27:40 ERROR unit.postgresql/11.juju-log Cluster upgrade failed, ensure pre-upgrade checks are ran first.
unit-postgresql-11: 2025-03-21 01:27:41 INFO juju.worker.uniter.operation ran "upgrade-charm" hook (via hook dispatching script: dispatch)
unit-postgresql-11: 2025-03-21 01:27:41 INFO juju.worker.uniter found queued "config-changed" hook
unit-postgresql-11: 2025-03-21 01:27:56 INFO unit.postgresql/11.juju-log PostgreSQL restart required
unit-postgresql-11: 2025-03-21 01:27:57 ERROR unit.postgresql/11.juju-log failed to change plugins:
Traceback (most recent call last):
File "/var/lib/juju/agents/unit-postgresql-11/charm/lib/charms/postgresql_k8s/v0/postgresql.py", line 354, in enable_disable_extensions
cursor.execute(
psycopg2.errors.UndefinedFile: could not open extension control file "/snap/charmed-postgresql/115/usr/share/postgresql/14/extension/pgaudit.control": No such file or directory

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/var/lib/juju/agents/unit-postgresql-11/charm/src/charm.py", line 1071, in enable_disable_extensions
self.postgresql.enable_disable_extensions(extensions, database)
File "/var/lib/juju/agents/unit-postgresql-11/charm/lib/charms/tempo_coordinator_k8s/v0/charm_tracing.py", line 1064, in wrapped_function
return callable(*args, **kwargs) # type: ignore
File "/var/lib/juju/agents/unit-postgresql-11/charm/lib/charms/postgresql_k8s/v0/postgresql.py", line 365, in enable_disable_extensions
raise PostgreSQLEnableDisableExtensionError() from e
charms.postgresql_k8s.v0.postgresql.PostgreSQLEnableDisableExtensionError
unit-postgresql-11: 2025-03-21 01:27:58 INFO juju.worker.uniter.operation ran "config-changed" hook (via hook dispatching script: dispatch)
unit-postgresql-11: 2025-03-21 01:28:00 INFO unit.postgresql/11.juju-log PostgreSQL restart required
unit-postgresql-11: 2025-03-21 01:28:02 INFO juju.worker.uniter.operation ran "secret-changed" hook (via hook dispatching script: dispatch)
unit-postgresql-11: 2025-03-21 01:28:05 INFO unit.postgresql/11.juju-log PostgreSQL restart required
unit-postgresql-11: 2025-03-21 01:28:06 INFO juju.worker.uniter.operation ran "secret-changed" hook (via hook dispatching script: dispatch)
unit-postgresql-11: 2025-03-21 01:28:08 INFO juju.worker.uniter.operation ran "secret-remove" hook (via hook dispatching script: dispatch)
unit-postgresql-11: 2025-03-21 01:28:09 INFO juju.worker.uniter.operation ran "restart-relation-changed" hook (via hook dispatching script: dispatch)
```

## Additional context

Noticed the snap is downrev 2 point releases, and held:

```
ubuntu@juju-bd78f7-stg-netbox-33:~$ snap info charmed-postgresql | tail -n 10
channels:
14/stable: 14.13 2024-10-09 (133) 186MB -
14/candidate: ^
14/beta: ^
14/edge: 14.17 2025-03-11 (155) 186MB -
16/stable: --
16/candidate: --
16/beta: --
16/edge: 16.8 2025-03-18 (161) 197MB -
installed: 14.11 (115) 185MB held
ubuntu@juju-bd78f7-stg-netbox-33:~$ _
```