fix: 只读checkbox应支持三种状态

public/web/sheet/sheet_common.js

@@ -501,7 +501,7 @@ var sheetCommonObj = {
     // 无法勾选的复选框
     getReadOnlyCheckBox () {
         function ReadOnlyCheckBox() {}
-        ReadOnlyCheckBox.prototype = new GC.Spread.Sheets.CellTypes.CheckBox();
+        ReadOnlyCheckBox.prototype = this.getCheckBox(true);
         ReadOnlyCheckBox.prototype.processMouseUp = function () {
             return;
         };