Remove TODO about normalizing calc() values at parse time for registered properties

This patch removes a TODO which states we should normalize calc() values
when parsing them for registered properties. I don't recall exactly why
I added this TODO but it doesn't seem that the spec says this needs to
be done. We already simplify calc() values in computation as per spec.

https://drafts.css-houdini.org/css-properties-values-api/

BUG=641877

Review-Url: https://codereview.chromium.org/2399803002
Cr-Commit-Position: refs/heads/master@{#423778}
1 file changed