Stop listing Python 2.7 in the README

We aren't explicitly dropping support, but we don't want to mislead users that everything works either (e.g. isort 5 preventing "Sort Imports" from working under Python 2.7).

Author: brettcannon

README.md

@@ -1,6 +1,6 @@
 # Python extension for Visual Studio Code
 
-A [Visual Studio Code](https://code.visualstudio.com/) [extension](https://marketplace.visualstudio.com/VSCode) with rich support for the [Python language](https://www.python.org/) (for all [actively supported versions](https://devguide.python.org/#status-of-python-branches) of the language: 2.7, >=3.6), including features such as IntelliSense, linting, debugging, code navigation, code formatting, Jupyter notebook support, refactoring, variable explorer, test explorer, snippets, and more!
+A [Visual Studio Code](https://code.visualstudio.com/) [extension](https://marketplace.visualstudio.com/VSCode) with rich support for the [Python language](https://www.python.org/) (for all [actively supported versions](https://devguide.python.org/#status-of-python-branches) of the language: >=3.6), including features such as IntelliSense, linting, debugging, code navigation, code formatting, Jupyter notebook support, refactoring, variable explorer, test explorer, snippets, and more!
 
 ## Quick start