Update .CONTRIBUTING.md

Co-authored-by: Erin Shaben <[email protected]>

Author: brunopgalvao

.CONTRIBUTING.md

@@ -73,7 +73,7 @@ Before making contributions, you need to set up the proper directory structure f
    # Fork polkadot-docs on GitHub first, then:
    git clone https://github.com/YOUR_USERNAME/polkadot-docs.git
    cd polkadot-docs
-   git checkout -b your-feature-branch
+   git checkout -b YOUR_FEATURE_BRANCH
    ```
 
    Your directory structure should now look like: