tls13: srv: Fix comment

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index ed9bdfb..5691835 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -1405,7 +1405,7 @@
 #endif
 
     /*
-     * We are negotiation the version 1.3 of the protocol. Do what we have
+     * We are negotiating the version 1.3 of the protocol. Do what we have
      * postponed: copy of the client random bytes, copy of the legacy session
      * identifier and selection of the TLS 1.3 cipher suite.
      */