fix various issues

- fix CI failure due to wrong usage of ticket_lifetime
- Improve document and comments

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index bb688b7..e7a4aef 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -933,7 +933,7 @@
 #if defined(MBEDTLS_HAVE_TIME)
         mbedtls_ms_time_t now = mbedtls_ms_time();
         mbedtls_ssl_session *session = ssl->session_negotiate;
-        /* The ticket age has been checked to be smaller that the
+        /* The ticket age has been checked to be smaller than the
          * `ticket_lifetime` in ssl_prepare_client_hello() which is smaller than
          * 7 days (enforced in ssl_tls13_parse_new_session_ticket()) . Thus the
          * cast to `uint32_t` of the ticket age is safe. */
@@ -2748,11 +2748,9 @@
     MBEDTLS_SSL_DEBUG_MSG(3,
                           ("ticket_lifetime: %u",
                            (unsigned int) session->ticket_lifetime));
-    if (session->ticket_lifetime >
-        MBEDTLS_SSL_TLS1_3_MAX_ALLOWED_TICKET_LIFETIME) {
-        /* TODO: Add new return value here? */
+    if (session->ticket_lifetime > 604800) {
         MBEDTLS_SSL_DEBUG_MSG(3, ("ticket_lifetime exceeds 7 days."));
-        return MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+        return MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER;
     }
 
     session->ticket_age_add = MBEDTLS_GET_UINT32_BE(p, 4);