[PATCH] Updating documentation about bulding documentation in Windows.

Current documentation contains outdated instruction and scripts relative to building documentation on Windows machine.

I removed useless scripts and wrote some guide to build docs using Windows Linux Subsystem.

Also, could be viewed on github - https://github.com/michail-nikolaev/postgres/commit/c6781351306810bfebab1fa5b454e8d24b9ea2f6

Thanks,

Michail.