fix: wrap string for translation

[richard015ar]

Issue: https://github.com/pressbooks/private/issues/2455

This pull request updates the way exclusion messages for interactive elements are handled in the pressbooks-shortcode-handler.php file. The main improvement is that these messages are now wrapped in a translation function, making them translatable for internationalization.

Internationalization improvements:

• Updated the exclusion message in the videopickerShortcodeHandler to use esc_html__() for translation support.
• Updated the exclusion message in the choosedatasetShortcodeHandler to use esc_html__() for translation support.
• Updated the exclusion message in the ohmQuestionShortcodeHandler to use esc_html__() for translation support.