assets.airspace.airspace: reduce opacity
assets.airspace.airspace: reduce opacity

Render the airspace more desaturated because previously it interfered
too much with flight tracks.

snip/skylines,Turbo87/skylines,Turbo87/skylines,TobiasLohner/SkyLines,RBE-Avionik/skylines,skylines-project/skylines,skylines-project/skylines,TobiasLohner/SkyLines,Harry-R/skylines,skylines-project/skylines,shadowoneau/skylines,RBE-Avionik/skylines,dkm/skylines,shadowoneau/skylines,kerel-fs/skylines,Harry-R/skylines,RBE-Avionik/skylines,Turbo87/skylines,dkm/skylines,dkm/skylines,shadowoneau/skylines,snip/skylines,skylines-project/skylines,Turbo87/skylines,shadowoneau/skylines,kerel-fs/skylines,Harry-R/skylines,Harry-R/skylines,TobiasLohner/SkyLines,dkm/skylines,snip/skylines,kerel-fs/skylines,RBE-Avionik/skylines