Fix animateColor test to work across browsers (web-platform-tests#4…

…5015)

Hi Team,

This PR is to update `animateColor` SVG animation tests from SVG1.1
suite to align with all browsers.

Blink removed it with following in 2014 - https://src.chromium.org/viewvc/blink?view=revision&revision=165071

Firefox / Gecko - never supported it (https://bugzilla.mozilla.org/show_bug.cgi?id=436296)
^ Since all use cases can be done via `animate`

Safari / WebKit - trying to remove - WebKit/WebKit#25671

Just raising this PR so we fix the tests on upstream as well, so on
next import, we don't have to fix them and all future engines importing
also align with other browsers.

Thanks!