docs: Fixed broken codesandbox link in the dev-docs (#6229)

fixed broken link

dev-docs/docs/introduction/contributing.mdx

@@ -20,7 +20,7 @@ Pull requests are welcome. For major changes, please [open an issue](https://git
 
 ### Option 2 - CodeSandbox
 
-1. Go to https://codesandbox.io/s/github/excalidraw/excalidraw
+1. Go to https://codesandbox.io/p/github/excalidraw/excalidraw
 1. Connect your GitHub account
 1. Go to Git tab on left side
 1. Tap on `Fork Sandbox`