Update Mbed TLS version to v3.4.0

Signed-off-by: Summer Qin <summer.qin@arm.com>
Change-Id: I48f9e8571eced25fe9eab3d1b85c27228dbc0d4c
diff --git a/tf-m-code-coverage.yaml b/tf-m-code-coverage.yaml
index 2851d1a..0195746 100644
--- a/tf-m-code-coverage.yaml
+++ b/tf-m-code-coverage.yaml
@@ -58,7 +58,7 @@
             No need to change.
       - string:
           name: 'MBEDTLS_VERSION'
-          default: 'mbedtls-3.3.0'
+          default: 'mbedtls-3.4.0'
           description: |
             Specify which MBEDTLS version to use
             refs/heads/<branch_name> : Pick up latest HEAD on branch