Fix "Similar code" issue in src/client/coding.js

[crcastle]

Similar code found in 1 other location (mass = 70)

https://codeclimate.com/github/crcastle/collaborative-code-conference/src/client/coding.js#issue_57036f5330dab00001143066

  anchor.addEventListener('click', function(e) {
    e.preventDefault();
    cm.setOption('theme', classPrefix);
    document.querySelector('#theme-button-text').innerHTML = 'Theme: ' + name;
    cm.focus();
  });

and

  anchor.addEventListener('click', function(e) {
    e.preventDefault();
    cm.setOption('mode', mime);
    document.querySelector('#language-button-text').innerHTML = 'Language: ' + name;
    cm.focus();
  });