Rename MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL to MBEDTLS_SSL_PROTO_TLS1_3

As we have now a minimal viable implementation of TLS 1.3,
let's remove EXPERIMENTAL from the config option enabling
it.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index d8467a4..0558ee0 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -1487,23 +1487,19 @@
 #define MBEDTLS_SSL_PROTO_TLS1_2
 
 /**
- * \def MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL
+ * \def MBEDTLS_SSL_PROTO_TLS1_3
  *
- * This macro is used to selectively enable experimental parts
- * of the code that contribute to the ongoing development of
- * the prototype TLS 1.3 and DTLS 1.3 implementation, and provide
- * no other purpose.
+ * Enable support for TLS 1.3.
  *
- * \warning TLS 1.3 and DTLS 1.3 aren't yet supported in Mbed TLS,
- *          and no feature exposed through this macro is part of the
- *          public API. In particular, features under the control
- *          of this macro are experimental and don't come with any
- *          stability guarantees.
+ * \note The support for TLS 1.3 is not comprehensive yet, in particular
+ *       pre-shared keys are not supported.
+ *       See docs/architecture/tls13-support.md for a description of the TLS
+ *       1.3 support that this option enables.
  *
- * Uncomment this macro to enable experimental and partial
- * functionality specific to TLS 1.3.
+ * Uncomment this macro to enable the support for TLS 1.3.
+ *
  */
-//#define MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL
+//#define MBEDTLS_SSL_PROTO_TLS1_3
 
 /**
  * \def MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE
@@ -1521,8 +1517,8 @@
  * recommended to set this option.
  *
  * Comment to disable compatibility mode for TLS 1.3. If
- * MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL is not enabled, this option does not
- * have any effect on the build.
+ * MBEDTLS_SSL_PROTO_TLS1_3 is not enabled, this option does not have any
+ * effect on the build.
  *
  */
 //#define MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE