Add 'helper text' pattern to replace success validation state

[hdrury1]

Subject Area(s):

Outside of the people picker we use green for the subject picker to show maximum subject area(s) selected. There is also a green stroke around the input but it appears inconsistently.

I propose we move to using a consistent "helper text" pattern. We will likely need to include some information below inputs throughout xPub as "information". This text is simply informing the user they cannot add any more, which fits the use of information/helper text instead of validation. It also removes the need for the distracting green stroke.