Delay when attempting to input Korean characters using an IME with certain types of text boxes

A user has reported that inputting Korean into certain types of text boxes in the editor using an IME results in delayed input. The user reports that this occurs with SMultiLineEditableTextBox in the SlateViewer or EditableTextBox(SEditableTextBox and SMultiLineEditableTextBox) in a Modal window.

The Windows IME for Korean was used to test this originally.

Regression?: No
This occurs in 4.18, 4.19, and 4.20

1. Open a project
2. Open the console and type in "debug crash" without the quotations
3. In the input field of the Crash Reporter Client, type some Korean characters (this can most easily be seen by holding down the "A" key)
   Result: There is a delay in the input for the keys
   Expected: There is no input delay