Update references to mbedtls_dev

Change these to point to the new mbedtls_framework module in the
framework submodule.

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/tests/scripts/audit-validity-dates.py b/tests/scripts/audit-validity-dates.py
index 96b705a..44b083d 100755
--- a/tests/scripts/audit-validity-dates.py
+++ b/tests/scripts/audit-validity-dates.py
@@ -29,8 +29,8 @@
 from generate_test_code import FileWrapper
 
 import scripts_path # pylint: disable=unused-import
-from mbedtls_dev import build_tree
-from mbedtls_dev import logging_util
+from mbedtls_framework import build_tree
+from mbedtls_framework import logging_util
 
 def check_cryptography_version():
     match = re.match(r'^[0-9]+', cryptography.__version__)