remove install and contribute sections

install leads people to install into the system instead of a virtualenv,
and readme isn't the place to teach that
contribute is now linked in the github interface above the readme

README.md

@@ -16,18 +16,6 @@ community that make adding new functionality easy.
 [Jinja]: https://jinja.palletsprojects.com/
 
 
-## Installing
-
-Install and update from [PyPI][] using an installer such as [pip][]:
-
-```
-$ pip install -U Flask
-```
-
-[PyPI]: https://pypi.org/project/Flask/
-[pip]: https://pip.pypa.io/en/stable/getting-started/
-
-
 ## A Simple Example
 
 ```python
@@ -47,14 +35,6 @@ $ flask run
 ```
 
 
-## Contributing
-
-For guidance on setting up a development environment and how to make a
-contribution to Flask, see the [contributing guidelines][].
-
-[contributing guidelines]: https://github.com/pallets/flask/blob/main/CONTRIBUTING.rst
-
-
 ## Donate
 
 The Pallets organization develops and supports Flask and the libraries