ci: Drop obsolete -Wno-error= stanzas

No corresponding warnings left. Tighten the screws to prevent new
warnings from creeping in.

v2:
* The debian-clang-release job still needs
  -Wno-error=sometimes-uninitialized.
v3:
* Drop more from debian-arm64-asan & debian-testing-msan jobs.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34799>
1 file changed