Update and rename NNNN-UTCClock.md to 0027-UTCClock.md (#1346)

Author: itingliu

Proposals/NNNN-UTCClock.md renamed to Proposals/0027-UTCClock.md

@@ -4,7 +4,7 @@
 * Authors: [Philippe Hausler](https://github.com/phausler)
 * Review Manager: [Tina L](https://github.com/itingliu)
 * Status: Review: Jun 10...Jun 17, 2025
-* Implementation: Pending
+* Implementation: [Pull request](https://github.com/swiftlang/swift-foundation/pull/1344)
 * Review: [Pitch](https://forums.swift.org/t/pitch-utcclock/78018) 
 
  ## Introduction
@@ -110,4 +110,4 @@ It was considered to add a new `Instant` type instead of depending on `Date` how
 
 It was considered to add a near-miss overload for `duration(to:)` that had an additional parameter of `includingLeapSeconds` this was dismissed because it was considered to be too confusing and may lead to bugs where that data was not intended to be used. 
 
-[^utclist] If there are any updates to the list that will be considered a data table update and require a change to Foundation.
+[^utclist] If there are any updates to the list that will be considered a data table update and require a change to Foundation.