0.12 follow up license fixes

[kevinjqliu]

From the vote thread: https://lists.apache.org/thread/g6strrb3vmtg3yp8fqw6mrwt32gnvv8p
Thanks @jbonofre

-- LICENSE
--- LICENSE in whl says the Thrift/Hive code is in vendor/fb303 and
vendor/hive_metastore. That's correct for the source distribution, but
in whl, it's actually located directly in fb303 and hive_metastore
(without vendor). So, the documentation is correct but the path is
not. It would be good to fix this.
--- The whl distributions bundle Cython 3.3.0 runtime code
(cython_runtime, __reduce_cython_ in the so lib). I checked: Cython is
Apache 2.0 license without NOTICE file. We should document Cython in
our LICENSE file (in the whl distributions)

[shaynhornik]

I'd like to pick this up. Plan: reword the fb303/hive_metastore entries in LICENSE so they are accurate for both layouts (vendor/ in the source distribution, top-level packages in wheels per the setup.py package_dir mapping), and add an entry documenting the Cython runtime code that the compiled extension modules embed in binary distributions. Will have a PR up shortly.

[jbonofre]

@shaynhornik sure! I will be happy to review 😄