removed c9 installation from readme (publiclab#8515)

README.md

@@ -40,7 +40,6 @@ We are developing a draft Roadmap for `plots2` and our broader Public Lab code p
 3. [Contributing](#contributing)
 4. [Prerequisites](#prerequisites)
 5. [Installation](#installation)
-    - [Simple Installation with Cloud9](https://github.com/publiclab/plots2/wiki/Simple-Installation-for-Cloud9)
     - [Standard Installation](#standard-installation)
     - [Windows Installation](#windows-installation)
 6. [SSL in Development](#ssl-in-development)
@@ -90,10 +89,6 @@ For installation, prerequisites include sqlite3 and rvm. [Click here for a compl
 
 ## Installation
 
-### Installation for Cloud9
-
-For information on how to install for use with the cloud environment, please see [here](https://github.com/publiclab/plots2/wiki/Simple-Installation-for-Cloud9).
-
 ### Standard Installation
 
 1. Fork our repo from https://github.com/publiclab/plots2.