Removed Flask Version Constraint

[guillaume-vignal]

Fixes: #583

Description

This PR removes the Flask version constraint (<2.3.0) from shapash as the underlying issue related to compatibility with dash has been resolved. The latest versions of dash now fully support Flask versions 2.3.0 and above.

Key Changes:

• Updated Flask Dependency: The restriction on Flask (Flask<2.3.0) has been removed.
• Tested with Latest Flask and Dash: Compatibility testing was done using the latest versions of both Flask and Dash to ensure the project works seamlessly with updated libraries.

Benefits:

• Security Improvements: Removing the version constraint allows the use of the latest Flask versions, which include important security updates.
• Compatibility: Users can now use shapash in environments where Flask versions 2.3.0 or above are required, improving flexibility.
• Performance Enhancements: Newer versions of Flask come with performance optimizations that the project can now benefit from.