Linux: Set app id without `.desktop` suffix

[guihkx]

Silences this startup warning given by Qt 6.5.2:

QGuiApplication::setDesktopFileName: the specified desktop file name ends with .desktop. For compatibility reasons, the .desktop suffix will be removed. Please specify a desktop file name without .desktop suffix

Here's the rationale, according to a Qt dev:

The desktop file name should not contain ".desktop" suffix, but some applications still specify it anyway because of the ambiguity in the documentation that was fixed in 0c5135a9dfa6140d23d86b001c3054891c22dcb9.

Source: https://codereview.qt-project.org/c/qt/qtbase/+/480688

[nuttyartist]

👍