Update CHANGELOG.md with Swift 5.6 release date (#42290)

Author: benrimmington

CHANGELOG.md

@@ -235,9 +235,12 @@ _**Note:** This is in reverse chronological order, so newer entries are added to
     return [ 1: "One", 2: "Two" ]
   }
   ```
+
 Swift 5.6
 ---------
 
+### 2022-03-14 (Xcode 13.3)
+
 * [SE-0327][]:
 
   In Swift 5 mode, a warning is now emitted if the default-value expression of an
@@ -466,8 +469,6 @@ Swift 5.6
   }
   ```
 
-**Add new entries to the top of this section, not here!**
-
 Swift 5.5
 ---------
 
@@ -886,8 +887,6 @@ Swift 5.5
   Asynchronous for loops use asynchronous sequences, defined by the protocol
   `AsyncSequence` and its corresponding `AsyncIterator`.
 
-**Add new entries to the top of this section, not here!**
-
 Swift 5.4
 ---------
 
@@ -1054,8 +1053,6 @@ Swift 5.4
   let _: Foo? = .bar.anotherFoo.getFoo().optionalFoo?.optionalFoo![]
   ```
 
-**Add new entries to the top of this section, not here!**
-
 Swift 5.3
 ---------