Update assembly Copyright notice to // comment

PiperOrigin-RevId: 275581634
diff --git a/src/f32-gemm/6x8-aarch64-neonfma-cortex-a73.S.in b/src/f32-gemm/6x8-aarch64-neonfma-cortex-a73.S.in
index a2f714e..2cd2003 100644
--- a/src/f32-gemm/6x8-aarch64-neonfma-cortex-a73.S.in
+++ b/src/f32-gemm/6x8-aarch64-neonfma-cortex-a73.S.in
@@ -1,7 +1,7 @@
-# Copyright 2019 Google LLC
-#
-# This source code is licensed under the BSD-style license found in the
-# LICENSE file in the root directory of this source tree.
+// Copyright 2019 Google LLC
+//
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree.
 
 #include <xnnpack/assembly.h>