Bump color_field to 3.0.

We have some users reporting issues with the color_field module on version 2.5:

Deprecated function: Implicit conversion from float 8.5 to int loses precision in Drupal\color_field\ColorRGB->getRed() (line 70 of modules/contrib/color_field/src/ColorRGB.php).

The newest version is 3.0 (see https://www.drupal.org/project/color_field/releases/3.0.0).

Affected websites will be fixed by using the newer module.