Remove MBEDTLS_THREADING_C check in check_test_dependencies

At the moment our tests only check for MBEDTLS_THREADIN_PTHREAD

Signed-off-by: Ryan Everett <ryan.everett@arm.com>
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 99c1d49..9191f65 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -1111,7 +1111,6 @@
     # No PSA equivalent - needed by some init tests
     echo "MBEDTLS_ENTROPY_NV_SEED" >> $expected
     # No PSA equivalent - required to run threaded tests.
-    echo "MBEDTLS_THREADING_C" >> $expected
     echo "MBEDTLS_THREADING_PTHREAD" >> $expected
 
     # Compare reality with expectation.