docs: fix small typo in documentation (#13545)

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### What?

Fixes a tiny typo in the documentation. 

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### Why?

### How?

Fixes #

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Co-authored-by: lstellway <lstellway@users.noreply.github.com>

packages/payload/src/uploads/types.ts

@@ -185,7 +185,7 @@ export type UploadConfig = {
    */
   externalFileHeaderFilter?: (headers: Record<string, string>) => Record<string, string>
   /**
-   * Field slugs to use for a compount index instead of the default filename index.
+   * Field slugs to use for a compound index instead of the default filename index.
    */
   filenameCompoundIndex?: string[]
   /**