docs: fix incorrect select syntax example in querying docs (#14590)

### What?

Fix incorrect select example in the querying docs. The docs showed
`select: [{ title: true }]` which is not valid. Updated to `select: {
title: true }` to match actual API usage and TypeScript types.

### Why?

The wrong example causes TypeScript errors and confusion for users.
Correcting it makes the docs accurate and consistent.

### How?

Updated the example in docs/queries/overview.mdx to use object syntax
for select. No code changes, documentation only.

Co-authored-by: Paul Popus <paul@payloadcms.com>

Author: syazwanz

docs/queries/overview.mdx

@@ -285,9 +285,9 @@ const posts = await payload.find({
   collection: 'posts',
   where: { ... },
   // highlight-start
-  select: [{
+  select: {
     title: true,
-  }],
+  },
   // highlight-end
 ```