docs(contributing): remove a duplicated opensource type (#5971)

contributing.md

@@ -50,7 +50,6 @@ Visit the following resources to learn more:
 - `@opensource@`
 - `@article@`
 - `@course@`
-- `@opensource@`
 - `@podcast@`
 - `@video@`
 
@@ -98,4 +97,4 @@ It's important to add a valid type, this will help us categorize the content and
   - Rewriting content in a way that doesn't add any value.
   - None English content.
   - PR's that don't follow our style guide, have no description and a default title.
-  - Links to your own blog articles.
+  - Links to your own blog articles.