Bump gson from 2.8.6 to 2.8.7

Bumps [gson](https://github.com/google/gson) from 2.8.6 to 2.8.7.
- [Release notes](https://github.com/google/gson/releases)
- [Changelog](https://github.com/google/gson/blob/master/CHANGELOG.md)
- [Commits](https://github.com/google/gson/compare/gson-parent-2.8.6...gson-parent-2.8.7)

Signed-off-by: dependabot[bot] <support@github.com>

app/build.gradle

@@ -273,7 +273,7 @@ dependencies {
     implementation "com.afollestad.material-dialogs:bottomsheets:${materialDialogsVersion}"
     implementation "com.afollestad.material-dialogs:lifecycle:${materialDialogsVersion}"
 
-    implementation 'com.google.code.gson:gson:2.8.6'
+    implementation 'com.google.code.gson:gson:2.8.7'
     implementation 'com.google.android.exoplayer:exoplayer:2.14.0'
 
     implementation 'com.github.chrisbanes:PhotoView:2.3.0'