CBOR: Remove dead code: len[12] are not used with UTF-16

The lengths are only needed to check if one of the two strings is empty
and in the direct 8-bit comparisons with memcmp(). So we don't need this
division by 2, which was here since the initial commit.

Amends d4c7da9a07.

Pick-to: 6.7
Change-Id: Ie28eadac333c4bcd8c08fffd17c5ecbce564ccd1
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

src/corelib/serialization/qcborvalue.cpp

@@ -1275,11 +1275,6 @@ static int compareElementRecursive(const QCborContainerPrivate *c1, const Elemen
     if (b1 || b2) {
         auto len1 = b1 ? b1->len : 0;
         auto len2 = b2 ? b2->len : 0;
-
-        if (e1.flags & Element::StringIsUtf16)
-            len1 /= 2;
-        if (e2.flags & Element::StringIsUtf16)
-            len2 /= 2;
         if (len1 == 0 || len2 == 0)
             return len1 < len2 ? -1 : len1 == len2 ? 0 : 1;