SDK: add wingpanel-9, remove unity (#150)

Author: danirabbit

elementary-sdk

@@ -31,8 +31,7 @@ Task-Metapackage: elementary-sdk
  * libgtk-4-dev
  * libhandy-1-dev
  * libswitchboard-3-dev
- * libunity-dev
- * libwingpanel-dev
+ * libwingpanel-9-dev
  * libxml2-dev
  * libxml2-utils
  * meson