Add missing HTTP global policy (#21691)

Author: maxvp

src/content/docs/cloudflare-one/policies/gateway/global-policies.mdx

@@ -42,3 +42,4 @@ The following policies are sorted by [order of precedence](/cloudflare-one/polic
 | Always Blocked Categories              | `00000001-bed5-462e-b0f1-2e2c3555e9f7` | Content Category | Child Abuse                                                        | block     | Blocks child abuse materials.                                                                                                                  |
 | Don't Isolate RBI Help Pages           | `00000001-1a18-431f-9c9d-bce431f1002a` | Hostname         | `developers.cloudflare.com` and `help.cloudflarebrowser.com`       | noisolate | Prevents browser isolation of Cloudflare developer docs and help pages to help users troubleshoot configuration issues.                        |
 | Don't AV Scan CF Speed                 | `00000001-c194-408f-87dd-9a366ce76e12` | Hostname         | `speed.cloudflare.com`                                             | noscan    | Allows files transferred by the Cloudflare speed test.                                                                                         |
+| Allow Gateway Services                 | `00000001-346f-4710-b444-eb62e369b5f7` | Destination IP   | Cloudflare Resolver IPs                                            | allow     | Ensures traffic can reach the block page when Gateway matches DNS Block policies.                                                              |