tests/api: Simplify 'default_headers' fixture
tests/api: Simplify 'default_headers' fixture

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