Update invocation.dart (#73)

Use `astFactory` instead of `new`.

Author: matanlurey

lib/src/builders/expression/invocation.dart

@@ -102,7 +102,7 @@ class _MethodInvocationBuilder extends Object
       $period,
       stringIdentifier(_method),
       _generics.isNotEmpty
-          ? new TypeArgumentList(
+          ? astFactory.typeArgumentList(
               $openBracket,
               _generics.map((t) => t.buildType(scope)).toList(),
               $closeBracket,