[release] Move DDC sync-async flip to correct section in the release notes

[email protected]

Change-Id: I0e3293ca1a7e13d79b2b59fb8500393ef4f0f5e5
Reviewed-on: https://dart-review.googlesource.com/53214
Reviewed-by: Alexander Thomas <[email protected]>

Author: athomas

CHANGELOG.md

@@ -29,6 +29,10 @@
   "as" cast failures on function types, and implicit cast failures on the above
   types and function types.)
 
+* `async` functions now start synchronously by default.  Build tools
+  (e.g., build_runner) may override the default and/or allow
+  developers to configure.
+
 ## 2.0.0-dev.51.0
 
 ### Tool Changes
@@ -38,12 +42,6 @@
   * Force splitting an empty block as the then body of an if with an else.
   * Uses the new lowercase Dart 2 constant names.
 
-#### Dart Dev Compiler
-
-* `async` functions now start synchronously by default.  Build tools
-  (e.g., build_runner) may override the default and/or allow
-  developers to configure.
-
 #### Pub
 
 * The `build` and `serve` commands will now fail and point users to