fix: rename Polykey vault target

Author: Brynley Llewellyn-Roux

flake.nix

@@ -19,7 +19,7 @@
             shellHook = ''
               echo "Entering $(npm pkg get name)"
               set -o allexport
-              . <(polykey secrets env js-timer)
+              . <(polykey secrets env js-async-cancellable)
               set +o allexport
               set -v
               ${lib.optionalString ci ''