ci/vkd3d: stop ignoring errors in a block where errors can't happen

The `if` will catch the exit code of what it calls (that's the whole point).

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

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

@@ -38,13 +38,11 @@ quiet() {
     set -x
 }
 
-set +e
 if ! vulkaninfo | tee /tmp/version.txt | grep -F "Mesa $MESA_VERSION";
 then
     printf "%s\n" "Found $(cat /tmp/version.txt), expected $MESA_VERSION"
     exit 1
 fi
-set -e
 
 if [ -d "$RESULTS" ]; then
     cd "$RESULTS" && rm -rf ..?* .[!.]* * && cd -