[🐛 BUG] Set content only available for strings making it unusable for Python API

[FlorianJacta]

What went wrong? 🤔

The doc says that set_content can only be used with strings making it impossible to change a page inside a notebook: https://docs.taipy.io/en/latest/refmans/reference/pkg_taipy/pkg_gui/Page/#taipy.gui.Page.set_content

Expected Behavior

This should also accept pages.

Version of Taipy

Taipy 4.0.2

Acceptance Criteria

• A unit test reproducing the bug is added.
• Any new code is covered by a unit tested.
• Check code coverage is at least 90%.
• The bug reporter validated the fix.
• Related issue(s) in taipy-doc are created for documentation and Release Notes are updated.

Code of Conduct

• I have checked the existing issues.
• I am willing to work on this issue (optional)