Fix leak of modulus structures in tests

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/suites/test_suite_bignum_random.function b/tests/suites/test_suite_bignum_random.function
index a837e1b..5064a62 100644
--- a/tests/suites/test_suite_bignum_random.function
+++ b/tests/suites/test_suite_bignum_random.function
@@ -208,7 +208,7 @@
                     &rnd_mod_raw, sizeof( rnd_mod_raw ) );
 
 exit:
-    mbedtls_mpi_mod_modulus_free( &N );
+    mbedtls_test_mpi_mod_modulus_free_with_limbs( &N );
     mbedtls_free( R_core );
     mbedtls_free( R_mod_raw );
 }