[Proposal] SF-0010 Rename accepted proposal (was previously NNNN)

Author: hristost

Proposals/NNNN-calendar-recurrence-rule-end-count-and-date.md renamed to Proposals/0010-calendar-recurrence-rule-end-count-and-date.md

@@ -1,7 +1,7 @@
 # Extending `Calendar.RecurrenceRule.End`
 
 
-* Proposal: SF-NNNN
+* Proposal: SF-0010
 * Author(s): Hristo Staykov <[email protected]>
 * Review Manager: [Tina Liu](https://github.com/itingliu)
 * Status: **Active review**