[13.x] FIX flaky dominantColor() test

[lucasmichot]

Fixes flaky test seen here: https://github.com/laravel/framework/actions/runs/30786125662/job/91599886845

Resizing to 1x1 can leave alpha slightly non-opaque depending on the image library version, so dominantColor() occasionally returned an 8-char hex instead of 6. Alpha is now dropped.

[jackbayliss]

Nice, I tried setting the alpha to see if that would work, but seems like it didnt

You can revert it here if you fancy it?

framework/tests/Image/Drivers/ImagickDriverTest.php

Line 497 in 251dc09

$imagick->setImageAlphaChannel(\Imagick::ALPHACHANNEL_OPAQUE);