all: update README

Author: hajimehoshi

README.md

@@ -2,7 +2,7 @@
 
 DebugUI is a UI toolkit for Ebitengine applications, primarily intended for debugging purposes.
 
-**The project is currently under development. The API is subject to frequent changes. Please do not use it in production.**
+**The project is currently under development. The API is subject to frequent changes.**
 
 DebugUI is based on [Microui](https://github.com/rxi/microui). The original Microui was developed by [@rxi](https://github.com/rxi/microui). The original Go port was developed by [@zeozeozeo](https://github.com/zeozeozeo) and [@Zyko0](https://github.com/Zyko0).