Bump kindest/node from v1.30.2 to v1.31.0 in /tests (nginx#2400)

Bumps kindest/node from v1.30.2 to v1.31.0.

---
updated-dependencies:
- dependency-name: kindest/node
  dependency-type: direct:production
...

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

Author: miledxz

tests/Dockerfile

@@ -1,3 +1,3 @@
 # syntax=docker/dockerfile:1.8
 # this is here so we can grab the latest version of kind and have dependabot keep it up to date
-FROM kindest/node:v1.30.2
+FROM kindest/node:v1.31.0