Fix variable PORTREVISION
Commit message:
```
commit df437c2165e72c01550c28b534735f1dbd5eb2af (HEAD -> main)
Author: Gabriel M. Dutra <dutra@FreeBSD.org>
Date: Sun Mar 3 12:05:46 2024 -0300
sysutils/bchunk: Fix PORTREVISION
Reported by: Ale <discipline@tiscali.it>
Approved by: dbaio (mentor), garga (mentor)
Fixes: 220062a3a1c35cc4deb0b363bdc27d09b492bf2e
```