ci/vkd3d: drop redundant "vkd3d-proton execution: SUCCESS"

The `+ exit 0` on the next line says the same thing, and we no longer
use that string for grepping the status anyway.

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

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

@@ -70,6 +70,4 @@ if ! /vkd3d-proton-tests/x64/bin/d3d12 > "$RESULTS/vkd3d-proton-log.txt"; then
     fi
 fi
 
-printf "%s\n" "vkd3d-proton execution: SUCCESS"
-
 exit 0