Update winui external plugin listing to v0.7.1 (#4325)

Co-authored-by: Nikola Metulev <711864+nmetulev@users.noreply.github.com>
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

plugins/external.json

@@ -1789,7 +1789,7 @@
   {
     "name": "winui",
     "description": "Agents and skills for WinUI 3 app development. Create new WinUI 3 desktop apps, convert from other frameworks (WPF, WinForms, Electron, Tauri, Flutter) to WinUI 3, or add features to existing WinUI 3 applications. Includes MSIX packaging, code signing, UI automation testing, and Windows App SDK guidance.",
-    "version": "0.7.0",
+    "version": "0.7.1",
     "author": {
       "name": "Microsoft",
       "url": "https://www.microsoft.com"
@@ -1813,8 +1813,8 @@
       "source": "github",
       "repo": "microsoft/win-dev-skills",
       "path": "plugins/winui/agent-plugin",
-      "ref": "v0.7.0",
-      "sha": "d4c103ba99abe145475abf87a6b25aad5b30fdd6"
+      "ref": "v0.7.1",
+      "sha": "2e8c902e9ba675e4c57550e066fc7e48b64c49b0"
     }
   }
 ]