Respond appropriately to textFormat changed

If the text has not changed when textFormat changes between states other
than RichText, the text was not re-laid-out. This is necessary if the
text includes control tags.

Task-number: QTBUG-31191
Change-Id: I3c6f5343aa85e8337b90cf86748a696d5742e906
Reviewed-by: Andrew den Exter <andrew.den.exter@qinetic.com.au>

src/quick/items/qquicktext.cpp

@@ -1989,6 +1989,7 @@ void QQuickText::setTextFormat(TextFormat format)
             d->rightToLeftText = d->extra->doc->toPlainText().isRightToLeft();
         } else {
             d->rightToLeftText = d->text.isRightToLeft();
+            d->textHasChanged = true;
         }
         d->determineHorizontalAlignment();
     }