tf-a-lts2.8: Upgrade mbedTLS to 3.6.0

Change-Id: I86db9bcb8c2125a8b86b34e87d7110cd8e020b9f
Signed-off-by: Yann Gautier <yann.gautier@st.com>
diff --git a/tf-a-lts2.8-main.yaml b/tf-a-lts2.8-main.yaml
index 47fc832..78a3d8f 100644
--- a/tf-a-lts2.8-main.yaml
+++ b/tf-a-lts2.8-main.yaml
@@ -44,7 +44,7 @@
             default: '+refs/heads/lts-v2.8:refs/remotes/origin/lts-v2.8'
         - string:
             name: MBEDTLS_URL
-            default: 'https://github.com/Mbed-TLS/mbedtls/archive/mbedtls-2.28.8.tar.gz'
+            default: 'https://github.com/Mbed-TLS/mbedtls/archive/mbedtls-3.6.0.tar.gz'
         - string:
             name: LAVA_RETRIES
             default: 2