gh-actions: Specify FreeBSD as 15.0

Signed-off-by: Daniel Schaefer <dhs@frame.work>

Author: JohnAZoidberg

.github/workflows/ci.yml

@@ -12,6 +12,9 @@ jobs:
     - name: Build
       id: test
       uses: vmactions/freebsd-vm@v1
+      with:
+        release: "15.0"
+        arch: x86_64
       with:
         usesh: true
         mem: 8192