cmd/govulncheck/integration: update go in integration tests

Change-Id: Ie85bcb40d8277b9e91bf08fe2b5d126350f4b76b
Reviewed-on: https://go-review.googlesource.com/c/vuln/+/589915
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Zvonimir Pavlinovic <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Maceo Thompson <[email protected]>

cmd/govulncheck/integration/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.20.3-alpine
+FROM golang:1.22.3-alpine
 
 # This Dockerfile sets up an image for repeated integration testing.
 # This assumes the build context, i.e., CWD is vuln/