Move copyright notice out of the Doxygen documentation

Signed-off-by: Gilles Peskine <[email protected]>

include/mbedtls/constant_time.h

@@ -1,6 +1,7 @@
 /**
  *  Constant-time functions
- *
+ */
+/*
  *  Copyright The Mbed TLS Contributors
  *  SPDX-License-Identifier: Apache-2.0
  *

include/mbedtls/legacy_or_psa.h

@@ -2,6 +2,8 @@
  *  Macros to express dependencies for code and tests that may use either the
  *  legacy API or PSA in various builds; mostly for internal use.
  *
+ */
+/*
  *  Copyright The Mbed TLS Contributors
  *  SPDX-License-Identifier: Apache-2.0
  *