update rootlesskit to v0.14.0

full diff: https://github.com/rootless-containers/rootlesskit/compare/v0.13.1...v0.14.0

v0.14.0 Changes (since v0.13.2)
--------------------------------------

- CLI: improve --help output
- API: support GET /info
- Port API: support specifying IP version explicitly ("tcp4", "tcp6")
- rootlesskit-docker-proxy: support libnetwork >= 20201216 convention
- Allow vendoring with moby/sys/mountinfo@v0.1.3 as well as @v0.4.0
- Remove socat port driver
    - socat driver has been deprecated since v0.7.1 (Dec 2019)
- New experimental flag: --ipv6
    - Enables IPv6 routing (slirp4netns --enable-ipv6). Unrelated to port driver.

v0.13.2
--------------------------------------

- Fix cleaning up crashed state dir
- Update Go to 1.16
- Misc fixes

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit e166af959d)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

hack/dockerfile/install/rootlesskit.installer

@@ -1,7 +1,7 @@
 #!/bin/sh
 
-# v0.13.1
-: "${ROOTLESSKIT_COMMIT:=5c30c9c2586add2ad659132990fdc230f05035fa}"
+# v0.14.0
+: "${ROOTLESSKIT_COMMIT:=81d7d047d09a5b93645817ec580181de7a984082}"
 
 install_rootlesskit() {
 	case "$1" in