ci/openbsd: update to 7.8

Update to cross-platform-actions 0.30.0.

.github/workflows/build.yml

@@ -428,10 +428,10 @@ jobs:
     steps:
     - uses: actions/checkout@v4
     - name: Test in OpenBSD VM
-      uses: cross-platform-actions/action@v0.29.0
+      uses: cross-platform-actions/action@v0.30.0
       with:
         operating_system: openbsd
-        version: '7.7'
+        version: '7.8'
         run: |
             sudo pkg_add -U \
                 cmake \
@@ -474,7 +474,7 @@ jobs:
     steps:
     - uses: actions/checkout@v4
     - name: Test in FreeBSD VM
-      uses: cross-platform-actions/action@v0.29.0
+      uses: cross-platform-actions/action@v0.30.0
       with:
         operating_system: freebsd
         version: '14.3'