After changing my Rails Version to 6.0.3.5 from 6.1.3 for Heroku. I have got a Runtime Error after running Rails S

When deploying basic app for the first time to Heroku I had to change my Rails Version to 6.0.3.5 from 6.1.3 because Heroku wasn't working on Rails 6.1.3. After changing the version to 6.0.3.5 in the Gemfile and running "bundle" and "bundle update". I am getting a Runtime error as attached. I am a beginner, help to right direction would be great.