Merge #16483: doc: update Python command in msvc readme

e0324c3 Updated python command in readme so it will work on systems that have both python2 and 3 installed. (Aaron Clauson)

Pull request description:

  Trivial doc update to the msvc build readme. It updates the python command to use the `py` python launcher so that it will work where Python2 & 3 are installed and 2 is the default (the msvc generator script is incompatible with Python 2).

Top commit has no ACKs.

Tree-SHA512: d7028d1ce4f3132e6b03a02f07ab2464eb946b603e0d46ef5c64882f3a99283602cf61f60e0c3a9c2836767b03222c8f37a9e7bfafda329cf7083f79235b2c65

Author: fanquake

build_msvc/README.md

@@ -44,7 +44,7 @@ The instructions below use `vcpkg` to install the dependencies.
 - Use Python to generate *.vcxproj from Makefile
 
 ```
-    PS >python msvc-autogen.py
+    PS >py -3 msvc-autogen.py
 ```
 
 - Build in Visual Studio.