Revert reference docs for ambient capabilities

This feature was reverted for docker 1.13
in c5251f7116e3d9095a7169fc31bd170dff997c2e,
so removing the documentation as well.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

docs/reference/run.md

@@ -1238,10 +1238,6 @@ since Docker 1.12. In Docker 1.10 and 1.11 this did not happen and it may be nec
 to use a custom seccomp profile or use `--security-opt seccomp=unconfined` when adding
 capabilities.
 
-It is only possible to grant capabilities to a container running as a user other than `root`
-on a system with a Linux kernel version of 4.3 or later, as this requires "ambient capabilities"
-to be granted. These will be added if the kernel allows it from Docker version 1.13.
-
 ## Logging drivers (--log-driver)
 
 The container can have a different logging driver than the Docker daemon. Use