title: deleted yarn.lock and commit changes but still getting lockfiles error
body: <p>I deleted yarn.lock and commit changes but still getting lockfiles error.     </p>
  
  <pre><code>  Counting objects: 24375, done.
          Delta compression using up to 4 threads.
          Compressing objects: 100% (17171/17171), done.
          Writing objects: 100% (24375/24375), 30.34 MiB | 1.03 MiB/s, done.
          Total 24375 (delta 6150), reused 23977 (delta 5909)
          remote: Compressing source files... done.
          remote: Building source:
          remote: 
          remote: -----&gt; Node.js app detected
          remote: 
          remote: -----&gt; Build failed
          remote:  !     Two different lockfiles found: package-lock.json and yarn.lock
          remote: 
          remote:        Both npm and yarn have created lockfiles for this application,
          remote:        but only one can be used to install dependencies. Installing
          remote:        dependencies using the wrong package manager can result in missing
          remote:        packages or subtle bugs in production.
          remote: 
          remote:        - To use npm to install your application's dependencies please delete
          remote:          the yarn.lock file.
          remote: 
          remote:          $ git rm yarn.lock
          remote: 
          remote:        - To use yarn to install your application's dependences please delete
          remote:          the package-lock.json file.
          remote: 
          remote:          $ git rm package-lock.json
          remote:     
          remote:        https://kb.heroku.com/why-is-my-node-js-build-failing-because-of-conflicting-lock-files
          remote: 
          remote:  !     Push rejected, failed to compile Node.js app.
          remote: 
          remote:  !     Push failed
          remote: Verifying deploy...
          remote: 
          remote: !   Push rejected to weight-tracker-react-rails.
          remote: 
  </code></pre>
  
  <p>To <a href="https://git.heroku.com/weight-tracker-react-rails.git" rel="nofollow noreferrer">https://git.heroku.com/weight-tracker-react-rails.git</a>
   ! [remote rejected]   master -> master (pre-receive hook declined)
  error: failed to push some refs to '<a href="https://git.heroku.com/weight-tracker-react-rails.git" rel="nofollow noreferrer">https://git.heroku.com/weight-tracker-react-rails.git</a></p>
  
  <p>'</p>