Remove outdated Heroku references from documentation

- Remove Live Demo section (Heroku free tier is gone)
- Remove Heroku deployment information from developer docs
- Heroku shut down free tier in 2022 and these links no longer work

Author: mircealungu

docs/README.rst

@@ -67,14 +67,6 @@ Adding the extension to your Flask app is simple:
     app = Flask(__name__)
     dashboard.bind(app)
 
-Live Demo
-------------
-To view a live deployment of the Flask-MonitoringDashboard, `check this site`_
-
-.. _`check this site`: https://flask-monitoringdashboard.herokuapp.com/
-
-Use the credentials u:`admin`, p:`admin` to log in.
-
 Feedback
 ------------
 In order to improve our Flask-MonitoringDashboard, we would like to hear from you! Therefore, we made a questionnaire

docs/developing.rst

@@ -166,14 +166,6 @@ The following tools are used for helping the development of the Dashboard:
     corresponding feature has been merged into the development branch. It is recommended to often
     merge development into this branch, to keep the feature branch up to date.
 
-- **Heroku deployment**: The following branches are automatically deployed to Heroku. This is useful for quickly
-  testing, without running any code locally.
-
-   - **Master**: The master branch is deployed at: `<https://fmd-master.herokuapp.com>`_.
-   - **Development**: The development is deployed at: `<https://fmd-development.herokuapp.com>`_.
-   - **Pull requests**: Pull requests are also automatically build with a unique URL.
-
-
 - **Unit testing**: The code is tested before a Pull Request is accepted. If you want to run the unit
   tests locally, you can use the following command from the root of Flask-MonitoringDashboard
   directory: