Move Robolectric snapshot repository config to common_library_config

This means it gets pulled in when apps depend on ExoPlayer locally:
https://github.com/google/ExoPlayer/blob/release-v2/README.md#locally

This resolves the missing snapshot error that people see currently,
because the existing repository config is in the top-level ExoPlayer
build.gradle file which isn't executed when depending on ExoPlayer
locally.

Issue: #8332
Issue: #7932
PiperOrigin-RevId: 347245078

build.gradle

@@ -26,7 +26,6 @@ allprojects {
     repositories {
         google()
         jcenter()
-        maven { url "https://oss.sonatype.org/content/repositories/snapshots" }
     }
     project.ext {
         exoplayerPublishEnabled = false

common_library_config.gradle

@@ -15,6 +15,12 @@
 apply from: "$gradle.ext.exoplayerSettingsDir/constants.gradle"
 apply plugin: 'com.android.library'
 
+repositories {
+    // TODO(internal b/169753382): Remove this when we no longer depend on
+    // Robolectric snapshots.
+    maven { url "https://oss.sonatype.org/content/repositories/snapshots" }
+}
+
 android {
     compileSdkVersion project.ext.compileSdkVersion