Update state of development

README.md

@@ -10,8 +10,8 @@ Based on [this repository](https://github.com/Mischa-Alff/imgui-backends) with b
 State of Development
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--   The [`master`](https://github.com/SFML/imgui-sfml/tree/master) branch contains work in progress supporting SFML 3. The SFML 3 API is not stable so this branch is not stable either.
--   The [`2.6.x`](https://github.com/SFML/imgui-sfml/tree/2.6.x) branch contains work targeting SFML 2 and is thus stable.
+Development is focused on version 3 in the `master` branch.
+No more features are planned for the 2.x release series.
 
 Dependencies
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