remove usage of Dart_New for paragraph/libtxt (#16837)

https://dart.googlesource.com/external/github.com/flutter/engine/+/c2fc31d19d5b4fce70b740f7802eb3b6ae2f4061
diff --git a/commits.json b/commits.json
index 89f857b..9b27843 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
-  "external/github.com/flutter/engine":"10da024fd61dba6d6a6f8fadb08aa5073c2d03ab",
+  "external/github.com/flutter/engine":"c2fc31d19d5b4fce70b740f7802eb3b6ae2f4061",
   "external/github.com/flutter/flutter":"55872847df891656863dd185906eab4d60d66a3e",
   "sdk":"566973afc039fefdf829783a75db94757c82c048"
 }
\ No newline at end of file