use latest mbedtls v3.6.3

Change-Id: I92fc728e301c256158d5a39087f80c40b857f1fa
Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
diff --git a/tf-a-gerrit-tforg-l2.yaml b/tf-a-gerrit-tforg-l2.yaml
index a1a4268..abe0493 100644
--- a/tf-a-gerrit-tforg-l2.yaml
+++ b/tf-a-gerrit-tforg-l2.yaml
@@ -58,7 +58,7 @@
               tf-a-job-configs refspec to use. The master branch is used by default.
         - string:
             name: MBEDTLS_URL
-            default: 'https://github.com/Mbed-TLS/mbedtls/archive/mbedtls-3.6.2.tar.gz'
+            default: 'https://github.com/Mbed-TLS/mbedtls/archive/mbedtls-3.6.3.tar.gz'
         - string:
             name: LAVA_RETRIES
             default: 2