EditableText: Do not treat "\r\n" as two characters when `backspace` is pressed (#12379)
In Notepad++, when hitting backspace to delete a line break, NVDA announces "blank" instead of "new line".
The TextInfo of the Scintilla implementation may contain "\r\n" instead of "\n".
The current implementation of EditableText._backspaceScriptHelper treats it as two characters and thus fails to trigger a proper announce.
Description of how this pull request fixes the issue:
Replace "\r\n" by "\n" before further treatment of the deleted chunk.