docs: whitespace culled
docs: whitespace culled

* lang/python/docs/gpgme-python-howto.org: Identified and fixed the
  headings which kept generating lines with trailing whitespace when
  exporting to Texinfo format and adjusted them to prevent that.

gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme