Updating readme in heroku setup and deployment guide

Title

Update readme in heroku setup and deployment guide

Documentation update

[ ] Feature (non-breaking change which adds functionality)
[ ] Bug Fix (non-breaking change that fixes an issue)
[ ] Breaking Change (feature/fix that causes existing features to not work as expected)
[x] Documentation

[x] I have read the [contribute]contributing doc
[x] Classes, scripts, and environment variables follow existing naming convention
[x] Lint and Unit tests pass locally
[ ] New features on hardware have been tested on a local Raspberry Pi
[ ] Mention new programs/binaries if any must be installed along with this change
[ ] Mention new environment variables if any have been added to hardware/env file
[x] Please make sure test coverage does not drop. If it does, please explain the reasons.
[ ] Any new required python modules are added to the requirements.txt