chore(ci): upgrade FreeBSD to 13.1

FreeBSD doesn't support /latest and /quarterly package repos on EOL
versions. 13.0 reaches EOL on 2022-08-31, so avoid CI breakage.

.github/workflows/freebsd.yml

@@ -11,7 +11,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - name: Test in FreeBSD VM
-      uses: vmactions/freebsd-vm@v0.1.6 # aka FreeBSD 13.0
+      uses: vmactions/freebsd-vm@v0.1.7 # aka FreeBSD 13.1
       with:
         mem: 2048
         usesh: true