remove unused libs caught by linter

Author: mykrupp

scripts/tools/silabs/factory_data_generator/custom.py

@@ -49,7 +49,7 @@ def custom_function(self):
 
 from cryptography.hazmat.backends import default_backend
 from cryptography.hazmat.primitives.serialization import load_der_private_key
-from default import Base64Argument, FileArgument, IntArgument, StrArgument
+from default import FileArgument
 
 
 class DacPKey(FileArgument):