Bump golang from 1.22 to 1.23 in /tests/conformance (#2401)

Bumps golang from 1.22 to 1.23.

---
updated-dependencies:
- dependency-name: golang
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

tests/conformance/Dockerfile

@@ -1,5 +1,5 @@
 # syntax=docker/dockerfile:1.8
-FROM golang:1.22
+FROM golang:1.23
 
 WORKDIR /go/src/github.com/nginxinc/nginx-gateway-fabric/tests/conformance