Remove non-effective color prop in ToggleButton

[chrismayer]

This removes non-effective color prop definition in the ToggleButton component.

[sronveaux]

Hi @chrismayer,

Just made the test and have to say that only one of the rules you removed is truly non-effective.

I prefer to let you see whether this should be amended or whether it should stay the same... but in this case, PR name should be changed as one of the removed lines IS still effective...

[fschmenger]

Maybe add @ntma as a reviewer and wait until he is around?
A lot of work and testing went into theming, so rather be sure there are no unintended side effects.

[chrismayer]

I just added the correction due to review comment by @sronveaux. Could you please give it another view and approve if you're happy now?

[sronveaux]

Looks perfect from my side and is ready to merge !

I let you appraise whether there is a chance to get @ntma comment on this... I suppose this can be changed again in the future in that case !

[chrismayer]

Thanks for your additional review @sronveaux. I am going to merge now, since I don't expect any problems by this changeset. @ntma If I am wrong, please comment here (even after merging) and I'll happily come up with separate PR.