Use ./x instead of ./x.py in documentation

[jyn514]

./x is the most likely to work on every system (on Unix it runs the shell script that does python version detection, on Windows it will probably run the powershell script - certainly less likely to break than ./x.py which often just opens the file in an editor).

This can be done with a simple find and replace, so it's a great first issue.

#1701 (comment)

[sslime336]

@jyn514 Hi, I'd like to do this :-) but I also found that in nushell using vscode on Win10 that typing ./x still just open the x.py, which acts like below:

If it's ok, I will also doc the exception which comes from myself

[sslime336]

@rustbot claim

[jyn514]

sounds good :) yes unfortunately there's nothing that's going to work on every platform, but i think ./x has a better chance of working than ./x.py.

[JohnTitor]

Addressed by #1710