DOC: Add instructions how to activate virtual env under windows with pip
Contributing.rst now correctly describes how to setup dev environment
under Windows when using pip and not conda.

Closes #29112

- [x] closes #29112 
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Hi @WillAyd ,
I've adjusted the comments as discussed above, please take a look when it is convenient to you

Regards @datapythonista mind taking a look here? Alright I need to apologize - yesterday I was tired and I've committed some brain fart to the repo.
What was missing was the information about the cmd.exe. Under Windows you can use two shells (WSL is a whole other story) - cmd.exe and powershell and they behave quite differently.

Now I've added the info about cmd.exe in the comments in the Windows code-block. Also I did some more testing with powershell and I've adjusted the initial generation of the virtual env, so that it 100% functions.

I've also added the `--no-use-pep517` argument to the Windows instructions, because it seems that under Windows a pep517 build gets triggered always. At least on the three different machines, I've tested with. Please see #28633 Hello, I did the requested changes

Regards Thanks @gbaychev 