Update module github.com/nginx/nginx-gateway-fabric/v2 to v2.1.4 (#3999)

| datasource | package                                  | from   | to     |
| ---------- | ---------------------------------------- | ------ | ------ |
| go         | github.com/nginx/nginx-gateway-fabric/v2 | v2.1.1 | v2.1.4 |

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

tests/go.mod

@@ -5,7 +5,7 @@ go 1.24.2
 replace github.com/nginx/nginx-gateway-fabric/v2 => ../
 
 require (
-	github.com/nginx/nginx-gateway-fabric/v2 v2.1.1
+	github.com/nginx/nginx-gateway-fabric/v2 v2.1.4
 	github.com/onsi/ginkgo/v2 v2.25.3
 	github.com/onsi/gomega v1.38.2
 	github.com/prometheus/client_golang v1.23.2