bump up rootlesskit to v0.9.4

Now `rootlesskit-docker-proxy` returns detailed error message on
exposing privileged ports: rootless-containers/rootlesskit#136

Full changes: rootless-containers/rootlesskit@v0.7.1...v0.9.4

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
(cherry picked from commit f6ac84163305e8b79a22f5910004321d0b5250e2)
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
Upstream-commit: 946d0ff67e1e277430ed86bd41d895eab059bab1
Component: engine

components/engine/hack/dockerfile/install/rootlesskit.installer

@@ -1,7 +1,7 @@
 #!/bin/sh
 
-# v0.7.1
-: ${ROOTLESSKIT_COMMIT:=76c4e26750da3986fa0e741464fbf0fcd55bea71}
+# v0.9.4
+: ${ROOTLESSKIT_COMMIT:=0fec9adac6b078aa8616da47e9d75f663ca3f492}
 
 install_rootlesskit() {
 	case "$1" in