ci: add path to go.sum to actions/setup-go

I just noticed that actions/setup-go complains about the missing
go.sum file:

>  Restore cache failed: Dependencies file is not found in /home/runner/work/sys/sys. Supported file pattern: go.sum

Apparently this happens because there's no top-level go.sum file.
Documentation[1] suggests using a wild card in such a case.

(The contents of these files are used as an input when calculating the
cache checksum, essentially meaning if any of these files are changed,
the cache will be invalidated.)

[1]: https://github.com/actions/setup-go/blob/main/README.md#caching-dependency-files-and-build-outputs

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

.github/workflows/test.yml

@@ -12,6 +12,7 @@ jobs:
       uses: actions/setup-go@v5
       with:
         go-version: ${{ matrix.go-version }}
+        cache-dependency-path: '**/go.sum'
     - name: Checkout code
       uses: actions/checkout@v4
     - if: ${{ matrix.go-version == '1.18.x' }}