ci: revert e2e Go pin to stable now that chainsaw/kuttl support Go 1.26

The e2e-k3d-chainsaw and e2e-k3d-kuttl jobs were pinned to Go 1.25.x with
a TODO noting that chainsaw/kuttl were missing the new testDeps.ModulePath
introduced by Go 1.26. Both projects have since shipped releases that
require go >= 1.26.0:
  * github.com/kudobuilder/kuttl v0.26.0  -> go 1.26.0
  * github.com/kyverno/chainsaw  (main)   -> go 1.26.0
actions/setup-go@v6 sets GOTOOLCHAIN=local when an explicit version is
requested, so the pinned 1.25.x runner cannot auto-upgrade to satisfy
those modules and the e2e jobs fail with:
  go: github.com/kudobuilder/kuttl/cmd/kubectl-kuttl@latest:
      github.com/kudobuilder/kuttl@v0.26.0 requires go >= 1.26.0
      (running go 1.25.9; GOTOOLCHAIN=local)
Switch both e2e jobs to 'go-version: stable', matching every other Go job
in the same workflow (go-test, kubernetes-api, kubernetes-k3d,
coverage-report). This unblocks the e2e checks that have been red on main
since the Go 1.26 bump landed in CrunchyData#4479.

Author: ValClarkson

.github/workflows/test.yaml

@@ -91,7 +91,7 @@ jobs:
     steps:
       - uses: actions/checkout@v6
       - uses: actions/setup-go@v6
-        with: { go-version: '1.25.x' } # TODO: revert to stable when chainsaw supports Go 1.26 (missing testDeps.ModulePath)
+        with: { go-version: stable }
 
       - name: Start k3s
         uses: ./.github/actions/k3d
@@ -142,7 +142,7 @@ jobs:
     steps:
       - uses: actions/checkout@v6
       - uses: actions/setup-go@v6
-        with: { go-version: '1.25.x' } # TODO: revert to stable when kuttl supports Go 1.26 (missing testDeps.ModulePath)
+        with: { go-version: stable }
 
       - name: Start k3s
         uses: ./.github/actions/k3d