tf-m-eclair-delta: Set MBEDTLS_VERSION to empty (detect from CMake files)

Following other jobs.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: Ia4dc967d99db505bb3af3954e4a5eca6e0f6ebb3
diff --git a/tf-m-eclair-delta.yaml b/tf-m-eclair-delta.yaml
index ad9f8df..7a71e6a 100644
--- a/tf-m-eclair-delta.yaml
+++ b/tf-m-eclair-delta.yaml
@@ -61,7 +61,7 @@
             No need to change.
       - string:
           name: 'MBEDTLS_VERSION'
-          default: 'mbedtls-3.4.0'
+          default: ''
           description: |
             Specify which MBEDTLS version to use
             refs/heads/<branch_name> : Pick up latest HEAD on branch