Replace placeholder with blurDataURL in global StaticImageData …

…type (#27916)

I think the global `StaticImageData` type does not currently match what actually gets imported, and what the `Image` component expects (see [here](https://github.com/vercel/next.js/blob/canary/packages/next/client/image.tsx#L60-L65)). This PR changes `placeholder` to `blurDataURL`.

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes

packages/next/image-types/global.d.ts

@@ -5,7 +5,7 @@ interface StaticImageData {
   src: string
   height: number
   width: number
-  placeholder?: string
+  blurDataURL?: string
 }
 
 declare module '*.png' {