docs: fix two "add" mistake in snapcraft.md (#27151)

docs/tutorial/snapcraft.md

@@ -83,7 +83,7 @@ snap(options)
 
 ### Step 1: Create Sample Snapcraft Project
 
-Create your project directory and add add the following to `snap/snapcraft.yaml`:
+Create your project directory and add the following to `snap/snapcraft.yaml`:
 
 ```yaml
 name: electron-packager-hello-world