ci: remove GitHub CI — native git.hanzo.ai + cd.hanzo.ai only

Inherited upstream workflow, repointed at a self-hosted ARC pool at fork time.
ARC is being decommissioned: CI runs inside git.hanzo.ai (Gitea Actions,
.hanzo/workflows) and delivery is cd.hanzo.ai reconciling the reviewed image
pin in hanzoai/universe. GitHub is a mirror and runs nothing.

This repo has no .hanzo/workflows today; it is a fork whose upstream CI we do
not rely on. If it needs a build, it gets a native pipeline — not an ARC pool.

.github/workflows/test-gateway-api-conformance.yaml

@@ -1,42 +0,0 @@
-name: Test K8s Gateway API conformance
-
-on:
-  pull_request:
-    branches:
-      - '*'
-    paths:
-      - '.github/workflows/test-gateway-api-conformance.yaml'
-      - 'pkg/provider/kubernetes/gateway/**'
-      - 'integration/fixtures/gateway-api-conformance/**'
-      - 'integration/gateway_api_conformance_test.go'
-      - 'integration/integration_test.go'
-
-env:
-  CGO_ENABLED: 0
-
-jobs:
-
-  test-gateway-api-conformance:
-    runs-on: hanzo-build-linux-amd64
-    timeout-minutes: 20
-
-    steps:
-      - name: Check out code
-        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
-        with:
-          fetch-depth: 0
-
-      - name: Set up Go
-        uses: actions/setup-go@7a3fe6cf4cb3a834922a1244abfce67bcef6a0c5 # v6.2.0
-        with:
-          go-version-file: '.go-version'
-          check-latest: true
-
-      - name: Avoid generating webui
-        run: |
-          touch webui/static/index.html
-
-      - name: Gateway API conformance test and report
-        run: |
-          make test-gateway-api-conformance
-          git diff --exit-code