Revert "pressure-vessel: Add support for the env var STEAM_COMPAT_FLAGS"
This reverts commit f32f230a.
Since the steam-runtime PR #439 the STEAM_COMPAT_FLAGS options are now a responsibility of run.sh
This MR should not be merged until either the steam-runtime PR https://github.com/ValveSoftware/steam-runtime/pull/439 has been released as the GA Steam Client, or the fallback implementation steamlinuxruntime!65 (merged) has landed in steamlinuxruntime.
Edited by Simon McVittie