Clarify ctx.query type on getServerSideProps (#20327)

Closes #19481

The current text implies `query` is a string. IMO it would be better if it clarified that `query` is an object containing the query string's keys and values

Edit:
Relevant docs url: https://nextjs.org/docs/basic-features/data-fetching#getserversideprops-server-side-rendering

docs/basic-features/data-fetching.md

@@ -633,7 +633,7 @@ The `context` parameter is an object containing the following keys:
 - `params`: If this page uses a dynamic route, `params` contains the route parameters. If the page name is `[id].js` , then `params` will look like `{ id: ... }`. To learn more, take a look at the [Dynamic Routing documentation](/docs/routing/dynamic-routes.md).
 - `req`: [The HTTP IncomingMessage object](https://nodejs.org/api/http.html#http_class_http_incomingmessage).
 - `res`: [The HTTP response object](https://nodejs.org/api/http.html#http_class_http_serverresponse).
-- `query`: The query string.
+- `query`: An object representing the query string.
 - `preview`: `preview` is `true` if the page is in the preview mode and `false` otherwise. See the [Preview Mode documentation](/docs/advanced-features/preview-mode.md).
 - `previewData`: The preview data set by `setPreviewData`. See the [Preview Mode documentation](/docs/advanced-features/preview-mode.md).
 - `resolvedUrl`: A normalized version of the request URL that strips the `_next/data` prefix for client transitions and includes original query values.