Xpra: Ticket #2571: hide opengl probe from macos dock

Despite setting LSUIElement to true (using a boolean since r25128), macos shows a dock icon for the opengl probe subprocess.

Either fix that or at least use a better dock icon than the default "folder" one that is used.

See also #2540

Thu, 06 Feb 2020 06:33:43 GMT - Antoine Martin: status, description changed

Sat, 23 Jan 2021 05:54:55 GMT - migration script:

this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/2571