tests/frontend: Simplify 'app' fixture
tests/frontend: Simplify 'app' fixture

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