[DataGrid] Fix broken "start editing" integration with Japanese (#5414)

Author: mnajdova

packages/grid/x-data-grid/src/utils/keyboardUtils.ts

@@ -13,8 +13,9 @@ export const isHomeOrEndKeys = (key: string): boolean => key === 'Home' || key =
 export const isPageKeys = (key: string): boolean => key.indexOf('Page') === 0;
 export const isDeleteKeys = (key: string) => key === 'Delete' || key === 'Backspace';
 
-const printableCharRegex = /^(\p{L}|\p{M}\p{L}|\p{M}|\p{N}|\p{Z}|\p{S}|\p{P})$/iu;
-export const isPrintableKey = (key: string) => printableCharRegex.test(key);
+// Non printable keys have a name, e.g. "ArrowRight", see the whole list:
+// https://developer.mozilla.org/en-US/docs/Web/API/UI_Events/Keyboard_event_key_values
+export const isPrintableKey = (key: string) => key.length === 1;
 
 export const GRID_MULTIPLE_SELECTION_KEYS = ['Meta', 'Control', 'Shift'];
 export const GRID_CELL_EXIT_EDIT_MODE_KEYS = ['Enter', 'Escape', 'Tab'];