lang/perl5*: remove calls to makewhatis

The @*exec macros have issues when being used when used with pkg -r,
as %D does not account for the root directory. As we have a periodic
task updating the makewhatis databases, and perl ports are the only ones
actually doing that, probably for some long lost historic reason, it is
easier to let that periodic task do its job.

PR: 280458
Discussed with: bapt
Reported by: Siva Mahadevan