fix(ci): pin vmactions/freebsd-vm to SHA for security audit

Security audit (scripts/security-audit.sh Layer 1) blocks unpinned
GitHub Actions. Pin vmactions/freebsd-vm@v1 to its release commit SHA.

Ref: scripts/security-audit.sh BLOCKED check
Signed-off-by: Pedro Ramos <131530838+pr9000@users.noreply.github.com>

Author: PR9000

.github/workflows/_build.yml

@@ -367,7 +367,7 @@ jobs:
 
       - name: Build FreeBSD ${{ matrix.release }} (${{ matrix.arch }}) binaries inside VM
         # https://github.com/vmactions/freebsd-vm
-        uses: vmactions/freebsd-vm@v1
+        uses: vmactions/freebsd-vm@83b151f58c6047089f4c80eb5ba2039d158ce093 # v1
         with:
           release: ${{ matrix.release }}
           arch: ${{ matrix.arch }}