Fix doxygen error for MBEDTLS_PLATFORM_ZEROIZE_ALT
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 85d3f8e..67ad4b2 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -2853,8 +2853,6 @@
 #define MBEDTLS_TLS_DEFAULT_ALLOW_SHA1_IN_KEY_EXCHANGE
 
 /**
- * \def MBEDTLS_PLATFORM_ZEROIZE_ALT
- *
  * Uncomment the macro to let mbed TLS use your alternate implementation of
  * mbedtls_platform_zeroize(). This replaces the default implementation in
  * platform_util.c.