Update build.gradle

[dintaaf]

2.7.0 not longer available on maven

[kntsappcompany]

Yes. Because of this, I can't use this library.

`

Could not find com.google.android.exoplayer:exoplayer:2.7.0.
Searched in the following locations:
- https://dl.google.com/dl/android/maven2/com/google/android/exoplayer/exoplayer/2.7.0/exoplayer-2.7.0.pom
- https://repo.maven.apache.org/maven2/com/google/android/exoplayer/exoplayer/2.7.0/exoplayer-2.7.0.pom
- https://jitpack.io/com/google/android/exoplayer/exoplayer/2.7.0/exoplayer-2.7.0.pom
- https://jcenter.bintray.com/com/google/android/exoplayer/exoplayer/2.7.0/exoplayer-2.7.0.pom
Required by:
project :app > com.github.mohan-dev1248:PosterSlider:1.0.2
`

Can we get an updated artifact which uses latest exoplayer? (2.19.1)