ci/freebsd: bump to FreeBSD 15.0

Author: llyyr

.github/workflows/build.yml

@@ -528,7 +528,7 @@ jobs:
       uses: cross-platform-actions/action@v0.32.0
       with:
         operating_system: freebsd
-        version: '14.3'
+        version: '15.0'
         run: |
             sudo pkg update
             sudo pkg install -y \