remove RESTRICTED from devel/p4 and devel/p4api

devel/p4 and devel/p4api are BSD licensed, even though the distfile does not
include any license file. The source for these ports is separately
distributed through swarm.workshop.perforce.com, and Perforce support
assures me that the license found in the source also applies to the binary
distfile used by these ports.

PR: 215662
Reviewed by: mat, gordon
Approved by: mat (ports)
Sponsored by: Spectra Logic Corp
Differential Revision: https://reviews.freebsd.org/D8623