misc/openvdb: builds fine in an armv7 jail on arm64

The process limimts have been revised in a fix to PR 274705, making
this port build fine.

PR: 274705
MFH: 2024Q2
Approved by: portmgr (build fix blanket)

(cherry picked from commit 12e7fdc3d5e4ef441fe41ad46978d4940ff991b4)