replace macos image assets

[chkuendig]

The currently logo has some diverging low-res assets:

This causes a glitch when starting the app:

This MR fixes the problem by replacing the asset with the original logo from https://github.com/transmission/transmission/blob/develop/macosx/Images/Transmission.icns

I'm aware of #1045 but since there's no movement on that I think it makes sense to fix the current icon first.

[chkuendig]

Not sure why this fails CI - it had the same issue with a broken lazarus installation, even before the change.Now it builds though on my machine

[PeterDaveHello]

@chkuendig thanks!

Just noticed that the commit message is a little bit too long for the commit subject, do you think you can shorten it? (Just put the details in the body)

Ref: https://chris.beams.io/posts/git-commit/

[chkuendig]

shortened it

[chkuendig]

Thanks for the encouragement, I encountered two separate issues though:

• I still can't reproduce the CI failure. It builds fine for me on a Mojave System with the dependencies from the build script. I can't build a working build at all on Catalina

• It actually seems there's one more asset affecting this, and this asset is actually part of the cross-platform transgui.ico (which uses the "frontal perspective" icon [ https://upload.wikimedia.org/wikipedia/commons/thumb/4/46/Transmission_Icon.svg/1200px-Transmission_Icon.svg.png ]). Would it make sense to keep this for all other platforms and only replace during build time (in that case I'll update the build script)? At the moment it's not really clear which should be the primary icon for transgui. I can also use the other icon (the "frontal" one) for all macOS icons.

PS: On second thought, maybe using

for all icons makes the most sense. Apple has also moved to much more "flatter" icons recently anyway. So I'd suggest to use this logo also for macOS unless there's any concerns. I'll update this MR in the next few days.

[PeterDaveHello]

hmmm, I'll take a look when I have enough time, thanks again.

[PeterDaveHello]

Sorry for the late reply, would like to see if #1045 is a go, and if so, maybe the problem here won't exist ;)