Improve documentation of MBEDTLS_SSL_KEEP_PEER_CERTIFICATE
/**
* \def MBEDTLS_SSL_KEEP_PEER_CERTIFICATE
*
- * This option controls the presence of the API mbedtls_ssl_get_peer_cert()
+ * This option controls the availability of the API mbedtls_ssl_get_peer_cert()
* giving access to the peer's certificate after completion of the handshake.
*
* Unless you need mbedtls_ssl_peer_cert() in your application, it is
