Editorial: Fix typo

Author: ptomato

spec/calendar.html

@@ -49,7 +49,7 @@ <h1>Abstract Operations</h1>
     <emu-clause id="sec-temporal-calendar-date-records">
       <h1>Calendar Date Records</h1>
       <p>
-        An <dfn variants="Calendar Date Records">Calendar Date Record</dfn> is a Record value used to represent a valid calendar date in a non-ISO 8601 calendar.
+        A <dfn variants="Calendar Date Records">Calendar Date Record</dfn> is a Record value used to represent a valid calendar date in a non-ISO 8601 calendar.
         Calendar Date Records are produced by the abstract operation CalendarISOToDate.
       </p>
       <p>Calendar Date Records have the fields listed in <emu-xref href="#table-temporal-calendar-date-record-fields"></emu-xref>.</p>