Prevent creation of Canvas pages in a non-default language in the UI/via the entity form
**Overview**
- Currently, when creating a new Canvas page, the language selector displays all languages configured on the website, including both the default language and translated languages.
- This behaviour allows users to create Canvas pages directly in non-default languages. However, Canvas pages should only be created in the site's default language (source language).
- For non-default languages, users should not create separate Canvas pages. Instead, translated content should be managed through the translation interface, where translations are entered against the source-language Canvas page.
**Proposed Solution**
- To align with the intended translation model, users should be prevented from creating Canvas pages in any language other than the site's default language.
- Remove dropdown from above the title field in the sidebar
issue