Simplify error message logic in ParseImportNames

test/message/import-as-reserved-word.out

Index: test/message/import-as-reserved-word.out
diff --git a/test/message/export-duplicate.out b/test/message/import-as-reserved-word.out
similarity index 51%
copy from test/message/export-duplicate.out
copy to test/message/import-as-reserved-word.out
index e88779f5805370e47565c87126674e4b934d7c19..1ee8d41c1afa3a77b0dd971ea4652a70a567317c 100644
--- a/test/message/export-duplicate.out
+++ b/test/message/import-as-reserved-word.out
@@ -1,7 +1,7 @@
 # Copyright 2015 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
-*%(basename)s:9: SyntaxError: Duplicate export of 'a'
-export { a, b };
-         ^
-SyntaxError: Duplicate export of 'a'
+*%(basename)s:7: SyntaxError: Unexpected reserved word
+import { foo as import } from "mod";
+                ^^^^^^
+SyntaxError: Unexpected reserved word