Remove `@tldraw/utils` from the docs site (#1596)

This PR removes the `@tldraw/utils` package from the docs site's API
reference. It does this by removing it from the docs site's
`devDependencies`.

The reason for this is this:

<img width="899" alt="Screenshot 2023-06-15 at 15 52 24"
src="https://github.com/tldraw/tldraw/assets/15892272/3b00e9da-663d-45e5-8b77-ab0a4fc466ad">


### Change Type

- [x] `documentation` — Changes to the documentation only[^2]

[^1]: publishes a `patch` release, for devDependencies use `internal`
[^2]: will not publish a new version

### Test Plan

1. Check the API Reference page of the docs.
2. Make that `@tldraw/utils` isn't there.

### Release Notes

- [docs] Removed an internal utilities package.

apps/docs/package.json

@@ -56,6 +56,11 @@
 		"rehype-slug-custom-id": "^1.1.0",
 		"remark-gfm": "^3.0.1"
 	},
+	"//": [
+		"Anything that starts with @tldraw in devDependencies will get included in the docs site.",
+		"We have to list them here so lazyrepo knows the docs depends on those packages (ie their",
+		"tsdoc comments), even though we don't use any of their code to run the docs site."
+	],
 	"devDependencies": {
 		"@microsoft/api-extractor-model": "^7.26.4",
 		"@tldraw/editor": "workspace:*",
@@ -65,7 +70,6 @@
 		"@tldraw/tldraw": "workspace:*",
 		"@tldraw/tlschema": "workspace:*",
 		"@tldraw/ui": "workspace:*",
-		"@tldraw/utils": "workspace:*",
 		"@tldraw/validate": "workspace:*",
 		"lazyrepo": "0.0.0-alpha.27",
 		"rimraf": "^4.4.0",