Fix eslint errors with PlaybackAPI.js and Settings.js

src/main/utils/PlaybackAPI.js

@@ -1,7 +1,7 @@
 import fs from 'fs';
 import mkdirp from 'mkdirp';
 
-var os = require('os');
+const os = require('os');
 
 const environment = process.env;
 

src/main/utils/Settings.js

@@ -2,7 +2,7 @@ import fs from 'fs';
 import mkdirp from 'mkdirp';
 import initalSettings from './initialSettings';
 
-var os = require('os');
+const os = require('os');
 
 const environment = process.env;