extmod/mbedtls: Remove MBEDTLS_ECP_DP_CURVE25519_ENABLED config.

Curve25519 arithmetic is supported in mbedtls, but it's not used for TLS.
So there's no need to have this option enabled.

Reduces rp2 PICO_W firmware by 2440 bytes.

Thanks to @Carglglz for the information.

Signed-off-by: Damien George <damien@micropython.org>

extmod/mbedtls/mbedtls_config_common.h

@@ -45,7 +45,6 @@
 #define MBEDTLS_ECP_DP_BP256R1_ENABLED
 #define MBEDTLS_ECP_DP_BP384R1_ENABLED
 #define MBEDTLS_ECP_DP_BP512R1_ENABLED
-#define MBEDTLS_ECP_DP_CURVE25519_ENABLED
 #define MBEDTLS_KEY_EXCHANGE_RSA_ENABLED
 // #define MBEDTLS_KEY_EXCHANGE_ECDHE_RSA_ENABLED // enabling this currently breaks ssl_data.py test
 #define MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED