Change Sink to Source in license header

library/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSinkFactory.java

 /*
 /*
- * Copyright (C) 2016 The Android Open Sink Project
+ * Copyright (C) 2016 The Android Open Source Project
  *
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * you may not use this file except in compliance with the License.