Changing the current font size in a QTextEdit doesn't update the size of the caret until you type

Steps to reproduce:

1. Build and run the attached test app "text-edit-caret-size-test".
2. Type some text in to the editor.
3. Change the font size with the spin box.
4. Observe that the caret doesn't change size.
5. Type some more text in the editor.
6. Now the caret changes size, and the new text is at the correct size.

Moving the cursor back through the document does change the caret correctly, so I think our users are reasonable to expect that it would change ahead of typing too.