mate-volume-control keyboard keys unsync with actual volume

[Yoan]

#### Expected behaviour
The keyboard keys "volume up" and "volume down" should always control the actual volume level of the current sound output.

#### Actual behaviour (see screenshot)
From time to time, the keyboard keys unsync from the actual level in the applet.
When the issue happens:
- The keyboard key icon (B) updates currently
- The volume level in the applet (blue rounded bar of A) **blinks** but the cursor (A) does not follow

A workaround to change volume is to move the A cursor directly, instead of using the keyboard keys.
Selecting another output usually causes the sync to work again, but going back to the first output still shows the issue.

#### Steps to reproduce the behaviour
Not easy to reproduce :'( since it happens after a few weeks of system uptime and a couple of changes of sound outputs (internal laptop, headset, external speakers, ...).

After system reboot, the sync usually works very well for several weeks of sound output changes, until it appears again and requires a reboot again.

#### MATE general version
1.26.0

#### Linux Distribution
5.15.0-107-generic #117-Ubuntu SMP Fri Apr 26 12:26:49 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
Ubuntu 22.04.4 LTS