Fix typos related to MessageDialog API (#17612)
Summary of the issue:
When a modal message dialog is open and we tried to use blocked actions like opening the NVDA's menu or the exit dialog, an error is raised
Description of development approach
• Fixed typo in _modalDialogOpenCallback method of source/gui/blockAction.py.
• Additionally, fixed capitalization of the confirm method in the developer guide.
Testing strategy:
Tested locally with clipContentsDesigner add-on, version 45.0.1 (dev channel), and opening message dialogs in the Python console, trying to activate the NVDA's menu or the exit dialog.
Known issues with pull request:
None
