.github/workflows: update govulncheck action

Change-Id: I2649a25b49b56fe42f89dc13ac3e445738a8a90c
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/508938
Reviewed-by: Sean Liao <[email protected]>
kokoro-CI: kokoro <[email protected]>
Auto-Submit: Sean Liao <[email protected]>
Reviewed-by: Julie Qiu <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Jamal <[email protected]>

Author: julieqiu

.github/workflows/govulncheck.yml

@@ -5,4 +5,4 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - id: govulncheck
-        uses: golang/govulncheck-action@v0.1.0
+        uses: golang/govulncheck-action@v1