clear some lint markers
OPEN - task 286: Add search option for courses 
https://github.com/DigitalCampus/oppia-mobile-android/issues/issue/286
OPEN - task 286: Add search option for courses 
https://github.com/DigitalCampus/oppia-mobile-android/issues/issue/286
OPEN - task 286: Add search option for courses 
https://github.com/DigitalCampus/oppia-mobile-android/issues/issue/286
OPEN - task 288: Search indexing - do as background task 
https://github.com/DigitalCampus/oppia-mobile-android/issues/issue/288
OPEN - task 288: Search indexing - do as background task 
https://github.com/DigitalCampus/oppia-mobile-android/issues/issue/288
OPEN - task 286: Add search option for courses 
https://github.com/DigitalCampus/oppia-mobile-android/issues/issue/286