fix: removed non valid option from README.md

Author: dfdez

README.md

@@ -113,7 +113,6 @@ When Git 2.18 or higher is not in your PATH, falls back to the REST API to downl
 
 - [Fetch only the root files](#Fetch-only-the-root-files)
 - [Fetch only the root files and `.github` and `src` folder](#Fetch-only-the-root-files-and-github-and-src-folder)
-- [Fetch only a single file](#Fetch-only-a-single-file)
 - [Fetch all history for all tags and branches](#Fetch-all-history-for-all-tags-and-branches)
 - [Checkout a different branch](#Checkout-a-different-branch)
 - [Checkout HEAD^](#Checkout-HEAD)
@@ -142,15 +141,6 @@ When Git 2.18 or higher is not in your PATH, falls back to the REST API to downl
       src
 ```
 
-## Fetch only a single file
-
-```yaml
-- uses: actions/checkout@v3
-  with:
-    sparse-checkout: |
-      /README.md
-```
-
 ## Fetch all history for all tags and branches
 
 ```yaml