Remove play-services-ads-identifier from IMA extension dependencies.

This is no longer needed since IMA depends on play-services-ads-identifier directly; see [article](https://ads-developers.googleblog.com/2019/12/the-interactive-media-ads-ima-sdk-for.html).

PiperOrigin-RevId: 401550793

extensions/ima/build.gradle

@@ -28,7 +28,6 @@ dependencies {
     api 'com.google.ads.interactivemedia.v3:interactivemedia:3.24.0'
     implementation project(modulePrefix + 'library-core')
     implementation 'androidx.annotation:annotation:' + androidxAnnotationVersion
-    implementation 'com.google.android.gms:play-services-ads-identifier:17.0.1'
     compileOnly 'org.checkerframework:checker-qual:' + checkerframeworkVersion
     compileOnly 'org.jetbrains.kotlin:kotlin-annotations-jvm:' + kotlinAnnotationsVersion
     androidTestImplementation project(modulePrefix + 'testutils')