Let's Encrypt Generation Y chains sign a P-256 leaf with the P-384
intermediate YE1 under ISRG Root YE. mqtt.meshtastic.org switched to
this chain on 2026-07-29. With CONFIG_MBEDTLS_ECP_DP_SECP384R1_ENABLED=n
mbedtls cannot parse the peer chain and the TLS handshake aborts with
MBEDTLS_ERR_PK_UNKNOWN_NAMED_CURVE, breaking MQTT over TLS on every
ESP32 target.
Costs about 4 kB of flash.
Fixes#11316
Thomas Göttgens
58657d484a