remove obsolete information from the README

Invoking "python3 setup.py install" directly is deprecated.

Remove entire "For packaging" paragraph. If anyone wants to package
ARver for a Linux distribution they will probably know how that should
be done.

Author: arcctgx

README.md

@@ -74,23 +74,14 @@ While the wheel is forward-compatible with future 3.x Python versions, the lates
 Python releases may not have been tested. The latest tested Python version is
 listed in the PyPI trove classifiers.
 
-For development:
+Use an editable installation for development and testing:
 
 ```sh
 git clone https://github.com/arcctgx/ARver
 cd ARver
 python3 -m pip install --editable .
 ```
 
-For packaging:
-
-```sh
-git clone https://github.com/arcctgx/ARver
-cd ARver
-python3 setup.py install --root=/tmp/pkg-arver
-# use contents of /tmp/pkg-arver to create a package.
-```
-
 ### Dependencies
 
 `ARver` depends on following Python packages at runtime: