ci/vkd3d: don't ignore errors

There was not even a matching `set -e` to restore the state afterwards,
so we just stopped caring about errors from that point forward.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29749>

.gitlab-ci/vkd3d-proton/run.sh

@@ -52,7 +52,6 @@ fi
 
 quiet printf "%s\n" "Running vkd3d-proton testsuite..."
 
-set +e
 if ! /vkd3d-proton-tests/x64/bin/d3d12 > "$RESULTS/vkd3d-proton.log";
 then
     # Check if the executable finished (ie. no segfault).