Dashboard: End date filter: make the Date form control inactive when the Comparator = "Is set" or "Is not set"

Overview:
In the Dashboard, when adding/editing a widget filter for "End date" when the Comparator = "Is set" or "Is not set", the "Date" form control should be inactive. Instead it is partially active.

Steps to Reproduce:

1. In the Dashboard app, select "New"
2. Set "Widget definition" = ERM Agreements
3. Set "Filter by" = End date
4. Set "Comparator" = Is set (or Is not set)
5. Select the keyboard TAB key - focus goes to the info popover
6. Select the TAB key again - focus goes to the "Today" radio button option
   Notice how it is not possible to tab to the second and third radio button options because they are inactive.

Expected Results:
As the Date form control is not relevant when the Comparator = "Is set" or "Is not set" the user should not be able to tab to the info popover or the "Today" option. the whole control should be inactive.

Note: if radio button 2 or 3 is selected before changing "Filter by" to "End date", when "End date" is selected the first radio button "Today" is not active. only the info popover is active.