Corrects documentation in ecdh.h

Commit corrects the documentation for
MBEDTLS_ECDH_LEGACY_CONTEXT in ecdh.h.

Signed-off-by: Thomas Daubney <thomas.daubney@arm.com>
diff --git a/include/mbedtls/ecdh.h b/include/mbedtls/ecdh.h
index 82d3de0..e5edb46 100644
--- a/include/mbedtls/ecdh.h
+++ b/include/mbedtls/ecdh.h
@@ -40,11 +40,7 @@
 
 #include "mbedtls/ecp.h"
 
-/**
- * \def MBEDTLS_ECDH_LEGACY_CONTEXT
- *
- * Use a backward compatible ECDH context.
- *
+/*
  * Mbed TLS supports two formats for ECDH contexts (#mbedtls_ecdh_context
  * defined in `ecdh.h`). For most applications, the choice of format makes
  * no difference, since all library functions can work with either format,
@@ -56,15 +52,8 @@
  * The new format is incompatible with applications that access
  * context fields directly and with restartable ECP operations.
  *
- * Define this macro if you enable MBEDTLS_ECP_RESTARTABLE or if you
- * want to access ECDH context fields directly. Otherwise you should
- * comment out this macro definition.
- *
  * This option has no effect if #MBEDTLS_ECDH_C is not enabled.
  *
- * \note This configuration option is experimental. Future versions of the
- *       library may modify the way the ECDH context layout is configured
- *       and may modify the layout of the new context type.
  */
 
 #if defined(MBEDTLS_ECP_RESTARTABLE)