Auto-complete should not be triggered inside the context of a char

When you start typing a string `"a string...`, auto-complete will correctly _not_ kick in. However, when you start typing a char like `'\r'`, this will auto-complete and select the first in the list (in this case `raise`), resulting in `'\raise'` after you hit the last `'`.

This also happens with any other potential name in the dropdown.


**Expected behavior**

The context of a string or char should not trigger auto-complete, but inside a char it happens anyway (string goes fine).

**Actual behavior**

Auto-complete is triggered and creates invalid chars.

**Extra info**

* It does not occur when there's no backslash involved
* Version: VS Prof 16.3.7.