Revert "fix(modal): check for overflow hidden"

[phazei]

This reverts commit 433e536.

This "fix" causes the general use case of being attached to the body to fail. This can be seen on the example site, past v2 the padding isn't added when it should be and the page 'jumps' when the scrollbar disappears.

This PR doesn't fix the original issue:
angular-ui#6037

But it does repair the general case which is more important than the edge case that's addressed.

[Morgul]

Hmm, interesting. This is a tough once, because both scenarios are "bad", but I do think that the fix in this case is a little worse than the bug.

I'm going to merge this, but only after opening a tracking bug for the original item, because I don't want to forget that this is here, or why I merged this in the first place.

[phazei]

The calculation for scrollbarPadding.heightOverflow does a lot of the same calculations as the isScrollable method. In addition to checking the overflow css values, it checks the clientHeight & scrollHeight and searches up the parent tree to find a scrollable parent. Perhaps that could be updated to handle the cases. Or isScrollable could be updated to handle a special case for body & html. Unfortunately I don't have the time to address that as well.