message: removed badges for travis - using only GitHub Actions and Appveyor now
diff: <td>
  master branch
  </td>
  - <td>
  - Linux/OSX <a href="https://travis-ci.org/onqtam/doctest"><img src="https://travis-ci.org/onqtam/doctest.svg?branch=master"></a>
  - </td>
  <td>
  Windows <a href="https://ci.appveyor.com/project/onqtam/doctest/branch/master"><img src="https://ci.appveyor.com/api/projects/status/j89qxtahyw1dp4gd/branch/master?svg=true"></a>
  </td>
  <td>
  dev branch
  </td>
  - <td>
  - Linux/OSX <a href="https://travis-ci.org/onqtam/doctest"><img src="https://travis-ci.org/onqtam/doctest.svg?branch=dev"></a>
  - </td>
  <td>
  Windows <a href="https://ci.appveyor.com/project/onqtam/doctest/branch/dev"><img src="https://ci.appveyor.com/api/projects/status/j89qxtahyw1dp4gd/branch/dev?svg=true"></a>
  </td>
  