Update ImageColumn.php

[KenKodz]

Remove the default of protected bool $header = false; in ImageColumn.php to reflect the default state as documented at https://ramonrietdijk.github.io/livewire-tables/usage/columns.html#header

[ramonrietdijk]

Hi @KenKodz,

Thank you for your contribution!

The documentation states that a header can be disabled. However, the documentation also states that image columns have their header disabled by default.

This change would also mean that projects that are currently using image columns would now need to add extra code which I don't really like.

That's why I'm unfortunately going to close this pull request.

[KenKodz]

Fair enough. I didn't see it in the image column docs. Thanks!