fix selection.affinity always downstream after updateEditingValue (#1682)

Co-authored-by: luying <[email protected]>

Author: Lamda303

lib/src/widgets/raw_editor/raw_editor_state_text_input_client_mixin.dart

@@ -203,7 +203,8 @@ mixin RawEditorStateTextInputClientMixin on EditorState
         diff.start,
         diff.deleted.length,
         diff.inserted,
-        value.selection,
+        value.selection.copyWith(
+            affinity: widget.configurations.controller.selection.affinity),
       );
 
       // if (widget.configurations.controller.selectedFontFamily != null) {