fix: update icon type check to use get_args for python 3.9 compatibility

[eharvey9s]

Description

Fixes issue #4758

Allows tabs to work with python 3.9+

Test Code

import flet as ft

def main(page: ft.Page):

    t = ft.Tabs(
        selected_index=1,
        animation_duration=300,
        tabs=[
            ft.Tab(
                text="Tab 1",
                content=ft.Container(
                    content=ft.Text("This is Tab 1"), alignment=ft.alignment.center
                ),
            ),
            ft.Tab(
                tab_content=ft.Icon(ft.Icons.SEARCH),
                content=ft.Text("This is Tab 2"),
            ),
            ft.Tab(
                text="Tab 3",
                icon=ft.Icons.SETTINGS,
                content=ft.Text("This is Tab 3"),
            ),
        ],
        expand=1,
    )

    page.add(t)

ft.app(main)

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist

• I signed the CLA.
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• New and existing tests pass locally with my changes
• I have made corresponding changes to the documentation (if applicable)

Screenshots

Additional details

Summary by Sourcery

Bug Fixes:

• Fix type checking for the icon property in the Tab control to ensure compatibility with Python 3.9+.

[CLAassistant]

All committers have signed the CLA.