Remove roundUp flag from formatTimeString function

So when you set e.g. 70 years ago in the To field of the date
range with "Round to the year" active, the To field's value is rounded
up. So instead of:

Jan 1, 1949 @ 00:00:00.000

It's

Jan 1, 1949 @ 23:59:59.999

Since now this date is less then 70 years in the past, moment.js fromNow
displays 69 years

src/components/date_picker/super_date_picker/date_popover/date_popover_button.js

@@ -48,7 +48,7 @@ export function EuiDatePopoverButton(props) {
       data-test-subj={`superDatePicker${position}DatePopoverButton`}
       {...buttonProps}
     >
-      {formatTimeString(value, dateFormat, roundUp)}
+      {formatTimeString(value, dateFormat)}
     </button>
   );