Improve role date selection

* Starting from 1700 and having to scroll all the way down to 2014, or even 2019, is painful
* Restrict date entries to current year rather than current year + 5 which seemed to be the default
* Refine copy about why roles cannot be changed later
I’m not sure this sentence still holds together with just a comma. I’m no content designer, but could I suggest using a semicolon instead?