netifaces requires vcpython27

[sajith]

I removed vcpython27 installation step from GitHub Actions in #3477, but missed the fact that netifaces has not published .whl packages for Python 2.7 and 64-bit Windows combination. This likely happened because netifaces was added after I created a branch for #3477.

See ​this CI run:

Running setup.py install for netifaces: started
    Running setup.py install for netifaces: finished with status 'error'
    ERROR: Complete output from command 'D:\a\tahoe-lafs\tahoe-lafs\.tox\py27-coverage\Scripts\python.EXE' -u -c 'import setuptools, tokenize;__file__='"'"'c:\\users\\runner~1\\appdata\\local\\temp\\pip-install-mfkv84\\netifaces\\setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record 'c:\users\runner~1\appdata\local\temp\pip-record-8kffce\install-record.txt' --single-version-externally-managed --compile --install-headers 'D:\a\tahoe-lafs\tahoe-lafs\.tox\py27-coverage\include\site\python2.7\netifaces':
    ERROR: running install
    running build
    running build_ext
    building 'netifaces' extension
    error: Microsoft Visual C++ 9.0 is required. Get it from http://aka.ms/vcpython27