python/meliae: Fix version string for download URL

While the version listed on PyPI is "0.4.0.final.0", the actual tarball
however is called just "meliae-0.4.0.tar.gz", which is the same *name*
(but different hash) as the one before the update in
7ce84830.

Here is the PyPI page for reference:

https://pypi.python.org/pypi/meliae/0.4.0.final.0



After checking the tarballs contents, the version string however *is*
"0.4.0.final.0", so I'm only changing the version in the download URL
rather than in the version attribute.

Signed-off-by: aszlig <aszlig@nix.build>
Cc: @FRidh