MacOSXPlatform: remove all "app-command" commands

Any command tagged with that attribute should be removed from the menus.
This is a more extensible approach than relying on the AppEventService
to inform of us every single such command.

See also:
https://github.com/scijava/scijava-common/commit/ca91f4e161558c8a90ce5ca7022f78453963d5fe
https://github.com/imagej/imagej-plugins-commands/commit/403d3e2afe771a9c13ca5edf95c8dba02843392f