Update skin preview images

[daschuer]

No description provided.

[ronso0]

unfortunately we can't use these screens: colors are not correct, library font is custom
See https://mixxx.zulipchat.com/#narrow/channel/109171-development/topic/2.2E5.2E0.20release.20deadline/near/490199318

[ronso0]

These are still the images with the screen calibration by @Eve00000 , ie. wrong colors.
See this diff for example

[ronso0]

Actually, the only difference 2.4 --> 2.5 I can spot at a glance in the previews are

• the new effect unit menu button
• no menubar anymore

Layout / features shown in the old screens is much better than the new ones.
After all the previews shoud give users an idea of the layout and colors, this is not a feature showcase like the press screenshots on the website.

= I'd rather keep the old previews than waiting for new polished ones.

(formally "requesting changes" so we don't merge the current state)

[ronso0]

.

[daschuer]

OK, works for me. I have just issued the version bump PR. #14049