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
(cherry picked from commit 776abb50435f102d055e1655fe1eada34993d2a0)

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'
 }