lts-v2.12: use mbedtls v3.6.3

Change-Id: Ib109ce7e75fd190e54542818c520186fe10e719f
Signed-off-by: Yann Gautier <yann.gautier@st.com>
diff --git a/tf-a-lts2.12-builder.yaml b/tf-a-lts2.12-builder.yaml
index f88ef89..89aef43 100644
--- a/tf-a-lts2.12-builder.yaml
+++ b/tf-a-lts2.12-builder.yaml
@@ -57,7 +57,7 @@
             default: 'http://releases.linaro.org/openembedded/aarch64/17.01/linaro-image-minimal-genericarmv8-20170127-888.rootfs.tar.gz'
         - 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: GERRIT_PATCHSET_NUMBER
             default: ''