lint: hoist stdlib imports above Import(env) in add_mbedtls_sources (#11172)

glob and os do not depend on the SCons-injected env, so importing them at
the top of the file removes the flake8 E402 findings and lets the E402
ignore-all directives (which were no longer suppressing anything) go away.

scripts/add_mbedtls_sources.py

@@ -10,13 +10,11 @@
 
 # trunk-ignore-all(ruff/F821)
 # trunk-ignore-all(flake8/F821): Import/env/Return are SCons-injected globals
-# trunk-ignore-all(ruff/E402)
-# trunk-ignore-all(flake8/E402): stdlib imports must follow Import("env")
-Import("env")
-
 import glob
 import os
 
+Import("env")
+
 framework_dir = env.PioPlatform().get_package_dir("framework-arduinopico")
 if not framework_dir:
     print("[add_mbedtls_sources] framework-arduinopico package not found - skipping")