Analyzer: regenerate diagnostics.md

Change-Id: If0d916b01d802fbdf614ee031f240094fb077931
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/151167
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Auto-Submit: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Paul Berry <paulberry@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

Author: srawlins

pkg/analyzer/tool/diagnostics/diagnostics.md

@@ -5554,6 +5554,9 @@ void f(int i) {
 
 ### return_of_invalid_type
 
+_A value of type '{0}' can't be returned from constructor '{2}' because it has a
+return type of '{1}'._
+
 _A value of type '{0}' can't be returned from function '{2}' because it has a
 return type of '{1}'._