devel/p5-Pod-Coverage: Add missing dependency

Add missing dependency on textproc/p5-Pod-Parser. Without it, the
following error is observed at runtime:

Can't locate Pod/Find.pm in @INC (you may need to install the Pod::Find module)

Reviewed by: koobs
Approved by: koobs (ports, mentor), portmgr (blanket: runtime fix)
Differential Revision: https://reviews.freebsd.org/D30274
MFH: 2021Q2 (missing dependency, runtime fix)