Remove unused imports (#2404)

Remove unused imports, as it is now part of ClassesRouter.js

Author: dharamgollapudi

src/Routers/InstallationsRouter.js

@@ -1,7 +1,6 @@
 // InstallationsRouter.js
 
 import ClassesRouter from './ClassesRouter';
-import PromiseRouter from '../PromiseRouter';
 import rest from '../rest';
 
 export class InstallationsRouter extends ClassesRouter {