onboarding: Add proper icon for action (#35241)

This change updates one icon within the onboarding flow to the indended
icon for that entry.

Release Notes:

- N/A

crates/onboarding/src/welcome.rs

@@ -32,8 +32,7 @@ const CONTENT: (Section<4>, Section<3>) = (
                 action: &Open,
             },
             SectionEntry {
-                // TODO: use proper icon
-                icon: IconName::Download,
+                icon: IconName::CloudDownload,
                 title: "Clone a Repo",
                 // TODO: use proper action
                 action: &NoAction,