Revert "use isolation characters instead of direction markers in cloze handling"

This reverts commit e838769d02.

Caused a regression:

https://anki.tenderapp.com/discussions/ankidesktop/41384-cloze-deletions-in-2125-and-2126

qt/ts/src/editor.ts

@@ -292,8 +292,8 @@ function wrapIntoText(front, back) {
 
 function wrapInternal(front, back, plainText) {
     if (currentField.dir === "rtl") {
-        front = "⁨" + front + "⁩";
-        back = "⁨" + back + "⁩";
+        front = "‫" + front + "‬";
+        back = "‫" + back + "‬";
     }
     const s = window.getSelection();
     let r = s.getRangeAt(0);