Remove Python 2 compatibility code.

[cristian-codorean]

Follow-up to #27, which set requires-python = ">=3.8": remove the Python 2 compatibility code that is now dead.

• Drop from __future__ import print_function.
• Flatten the py2/py3 try/except ImportError into plain urllib/http.client imports.
• Remove the import ssl guard: the module never uses ssl directly (urllib handles TLS), and sys.exit() at import time is hostile to embedding applications. Pythons built without SSL fail with a clear error on first HTTPS request anyway.
• Ignore303.redirect_request: use req.data / req.origin_req_host directly (the get_data()/get_origin_req_host() fallbacks were for Python < 3.4).
• Drop py2-style (object) bases.

No functional change intended. Verified locally: module compiles, imports, and the redirect handler preserves data/origin_req_host on 301/302 and returns None on 303, as before.

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