constraint properties should not be scoped to "source" only

[ShijunS]

[Section 14.1] In the “video” property table, the spec has the following for the "width" property, “The width or width range, in pixels, of the video source.”

Since constraints can be applied to track (not directly to the “source”), I’d suggest removing “of the video source”, so the definition becomes, "The width or width range in pixels."

There are two other places in the table, i.e. for "height" and "frameRate", which have the same issue.