python-future: FTBFS in Noble

As seen in the test rebuild:
https://people.canonical.com/~ginggs/ftbfs-report/test-rebuild-20231215-noble-noble.html

docs/translation.rst:89: CRITICAL: Title level inconsistent:

Known limitations of ``past.translation``
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/<<PKGBUILDDIR>>/docs/imports.rst:4: WARNING: Duplicate explicit target name: "here".
docs/unicode_literals.rst:144: CRITICAL: Title level inconsistent:

In favour of ``unicode_literals``
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docs/unicode_literals.rst:175: CRITICAL: Title level inconsistent:

Against ``unicode_literals``
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/<<PKGBUILDDIR>>/docs/pasteurize.rst:4: WARNING: duplicate label backwards-conversion, other instance in /<<PKGBUILDDIR>>/docs/automatic_conversion.rst
WARNING: autodoc: failed to import module 'standard_library' from module 'future'; the following exception was raised:
No module named 'imp'
/<<PKGBUILDDIR>>/.pybuild/cpython3_3.12_future/build/future/utils/__init__.py:docstring of future.utils.python_2_unicode_compatible:24: ERROR: Inconsistent literal block quoting.
WARNING: autodoc: failed to import module 'builtins' from module 'past'; the following exception was raised:
No module named 'imp'