fix: remove address: null from admission control testdata output

The CI YAML marshaling (Linux/amd64) omits nil *string fields while
local macOS/arm64 includes them as null. Remove address: null to match
CI's regenerated output and pass gen-check.

Co-authored-by: Cursor <cursoragent@cursor.com>
Signed-off-by: Adam Buran <aburan28@gmail.com>

Author: aburan28

internal/gatewayapi/testdata/backendtrafficpolicy-admission-control.out.yaml

@@ -122,8 +122,7 @@ infraIR:
   envoy-gateway/gateway-1:
     proxy:
       listeners:
-      - address: null
-        name: envoy-gateway/gateway-1/http
+      - name: envoy-gateway/gateway-1/http
         ports:
         - containerPort: 10080
           name: http-80