adds xpack.security.authc.selector.enabled setting

setting xpack.security.authc.selector.enabled introduced in 7.7.0 by #53010 is currently missing for docker entrypoint script

Author: jguay

src/dev/build/tasks/os_packages/docker_generator/resources/bin/kibana-docker

@@ -237,6 +237,7 @@ kibana_vars=(
     xpack.security.authc.oidc.realm
     xpack.security.authc.saml.realm
     xpack.security.authc.saml.maxRedirectURLSize
+    xpack.security.authc.selector.enabled
     xpack.security.cookieName
     xpack.security.enabled
     xpack.security.encryptionKey