[dart] Remove no-constant-update-2018, the underlying issue has been resolved.

Change-Id: I5d8c1199df37872d5f9fbef9c1eafc5c5ae89663
diff --git a/runtime/dart/dart_kernel.gni b/runtime/dart/dart_kernel.gni
index 885f5ca..11db035 100644
--- a/runtime/dart/dart_kernel.gni
+++ b/runtime/dart/dart_kernel.gni
@@ -143,10 +143,6 @@
 
     script = _compiler_path
     args += [
-             # TODO(https://github.com/dart-lang/sdk/issues/36639):
-             # Remove when new constant eval supports dilp files.
-             "--enable-experiment=no-constant-update-2018",
-
              "--target",
              invoker.platform_name,
              "--platform",