github/workflows: disable syncing files on freebsd

This option was just added to the new release tag so bump it to 0.20. We
don't care about syncing files, so disable it since it should prevent a
one type of error related to ejecting the hard drive*.

*: cross-platform-actions/action#64

.github/workflows/build.yml

@@ -176,9 +176,10 @@ jobs:
     steps:
     - uses: actions/checkout@v3
     - name: Test in FreeBSD VM
-      uses: cross-platform-actions/action@v0.19.1
+      uses: cross-platform-actions/action@v0.20.0
       with:
         operating_system: freebsd
+        sync_files: false
         version: '13.2'
         run: |
             sudo pkg update