docs: hotfix rename coder-ai readme to index (#17346)

[preview](https://coder.com/docs/@hotfix-ai-coder-top/)

Co-authored-by: EdwardAngert <17991901+EdwardAngert@users.noreply.github.com>

docs/manifest.json

@@ -670,7 +670,7 @@
 		{
 			"title": "Run AI Coding Agents in Coder",
 			"description": "Learn how to run and integrate AI coding agents like GPT-Code, OpenDevin, or SWE-Agent in Coder workspaces to boost developer productivity.",
-			"path": "./coder-ai/README.md",
+			"path": "./coder-ai/index.md",
 			"icon_path": "./images/icons/wand.svg",
 			"state": ["early access"],
 			"children": [