Raster Layer Styling forgets initial renderer settings

[Benjamin Jakimow]

The Raster Layer Styling panel fails to reset to the initial renderer.

How to reproduce:

1. Open Example Data “enmap” imae
2. Open Raster Layer Styling panel
3. Change to another renderer
4. Change back to RGB renderer. As the RGB setting has never been changed, it is expected that the image would be visualized in the same way as before step 3

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[Andreas Rabe]

https://github.com/EnMAP-Box/enmap-box/commit/72a4336edebc1ebbe1968eb260f5b3978e67a31f