ping @justincormack

@thaJeztah @justincormack Here is the fix for the CAP_SYS_NICE documentation.

@tfoxnc note that the associated change in moby was merged to master, but is not currently staged for 18.06

@thaJeztah @tfoxnc The current documentation is currently incorrect independently of the moby change.
If we wanted to have the documentation matching the current docker version, we will need this doc change + another change removing the references to "CAP_SYS_NICE gating system call" because before the moby fix, it is not the case.

@justincormack Could we merge this PR to fix this typo in the documentation?

Merging with @bermudezmt