Change multidex dependency type to androidTestImplementation

This is only needed for instrumentation tests and should not
be included in regular builds.

#minor-release

Issue: androidx/media#499
PiperOrigin-RevId: 545913113

RELEASENOTES.md

@@ -13,6 +13,8 @@
         and nullable array element types are not detected as nullable. Examples
         are `TrackSelectorResult` and `SimpleDecoder` method parameters
         ([6792](https://github.com/google/ExoPlayer/issues/6792)).
+    *   Remove accidentally added `multidex` dependency from all modules
+        ([#499](https://github.com/androidx/media/issues/499)).
 *   ExoPlayer:
     *   Add suppression of playback on unsuitable audio output devices (e.g. the
         built-in speaker on Wear OS devices) when this feature is enabled via

common_library_config.gradle

@@ -43,6 +43,6 @@ android {
 }
 
 dependencies {
-    implementation 'androidx.multidex:multidex:' + androidxMultidexVersion
+    androidTestImplementation 'androidx.multidex:multidex:' + androidxMultidexVersion
     coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.1.5'
 }