tools: revise install.py for minor improvements

* Use an with block for reading the config file.
Refs: https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files

* Use explicit blank return to make it clear that the return value is
  not actually used and that it is being used for flow control only..

PR-URL: https://github.com/nodejs/node/pull/36626


Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Christian Clauss <cclauss@me.com>