Comments on not needing to use ImDrawFlags_RoundCornersAll.

docs/CHANGELOG.txt

@@ -64,6 +64,7 @@ Breaking Changes:
      The new order is also more convenient as `flags` are less frequently used than `thickness` in real code.
    - As a general policy in Dear ImGui, all our flags default to 0 so ImDrawFlags_None was likely written 0 in some call sites.
    - Consider adding `#define IMGUI_DISABLE_OBSOLETE_FUNCTIONS` in your imconfig.h, even temporarily, to clean up legacy code.
+   - Reminder: you do NOT need to specify `ImDrawFlags_RoundCornersAll` for rounding, it is already the default!
 - DrawList: obsoleted `ImDrawCallback_ResetRenderState` in favor of using `ImGui::GetPlatformIO().DrawCallback_ResetRenderState`,
     which is part of our new standard draw callbacks. (#9378)
     Redirecting the earlier value into the later one when set, so both old and new code should work.