Add AI Gateway to integrations sidenav and adjust titles

Author: RebeccaTamachiro

src/content/docs/secrets-store/integrations/ai-gateway.mdx

@@ -0,0 +1,8 @@
+---
+pcx_content_type: navigation
+title: AI Gateway integration
+external_link: /ai-gateway/configuration/bring-your-own-keys/
+sidebar:
+  order: 3
+  label: AI Gateway
+---

src/content/docs/secrets-store/integrations/workers.mdx

@@ -1,9 +1,9 @@
 ---
-title: Use Secrets Store with Workers
+title: Workers integration
 pcx_content_type: tutorial
 sidebar:
   order: 1
-  label: Use with Workers
+  label: Workers
 ---
 
 import { WranglerConfig, Tabs, TabItem, APIRequest } from "~/components";