[libc++][NFC] Consistently use newline between license and include guard

NOKEYCHECK=True
GitOrigin-RevId: 480cd780d63fd9c658cc2f51d0c54416b8b1a5c3
diff --git a/include/filesystem b/include/filesystem
index 98d4bb9..7efa4ed 100644
--- a/include/filesystem
+++ b/include/filesystem
@@ -6,6 +6,7 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
+
 #ifndef _LIBCPP_FILESYSTEM
 #define _LIBCPP_FILESYSTEM