Fix typo in documentation

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/docs/architecture/tls13-support.md b/docs/architecture/tls13-support.md
index 6f766c9..fc09f31 100644
--- a/docs/architecture/tls13-support.md
+++ b/docs/architecture/tls13-support.md
@@ -476,7 +476,7 @@
 reduce the size of its code and to simplify it.
 
 * post-processing stage: following the parsing, further update of the SSL
-context to prepare for the next incoming and outpoing messages. This stage is
+context to prepare for the next incoming and outgoing messages. This stage is
 optional. For example, secret and key computations occur at this stage, as well
 as handshake messages checksum update.