Viewer shows pixel formats in the wrong order

[tpwrules]

Describe the bug
The viewer appears to show pixel formats in the wrong order.

To Reproduce
Steps to reproduce the behavior:

1. Plug in a camera
2. Select it in the viewer
3. Observe that (e.g.) the pixel formats listed are e.g. Mono12p, Mono12, and Mono8 (grayed out).
4. Start the camera stream with e.g. Mono12p selected
5. Observe that the stream starts properly
6. Select a different pixel format, then select Mono12p again
7. Start the camera stream
8. Observe that the stream does not start and Aravis prints the message GStreamer cannot understand this camera pixel format: 0x10c0047!

Expected behavior
I expect the pixel format selection to work properly.

Camera description:

• Basler
• acA2040-90umNIR
• USB3

Platform description:

• Aravis 0.8.25
• OS: Ubuntu 20.04
• x86_64

Additional context
In Aravis 0.8.24, the formats are listed in reverse of the order they appear in 0.8.25 and everything appears to work correctly.