sysutils/slurm-wlm: Fix: task/pgid plugin not installed

Running slurmd shows the following errors at startup:
slurmd: error: Couldn't find the specified plugin name for task/pgid looking at all files
slurmd: error: cannot find task plugin for task/pgid
slurmd: error: cannot create task context for task/pgid
slurmd: error: slurmd initialization failed

PR: 289384 288668
Fixes: 7bc4e1e182ec (Fix: TaskPlugin=task/pgid in slurm.conf fails on FreeBSD – plugin unavailable)
MFH: 2025Q3