GHA/non-native: bump to OpenBSD 7.8

Follow-up to e5cc5640b37672bd18d7561bc45c5dd91271753a #19367

Closes #19368
diff --git a/.github/workflows/non-native.yml b/.github/workflows/non-native.yml
index 523a676..19ff552 100644
--- a/.github/workflows/non-native.yml
+++ b/.github/workflows/non-native.yml
@@ -102,7 +102,7 @@
         with:
           environment_variables: MATRIX_ARCH
           operating_system: 'openbsd'
-          version: '7.7'
+          version: '7.8'
           architecture: ${{ matrix.arch }}
           run: |
             # https://openbsd.app/