Remove checkNotNull from Transformer build method.

PiperOrigin-RevId: 487811903

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/Transformer.java

@@ -402,16 +402,12 @@ public final class Transformer {
     /**
      * Builds a {@link Transformer} instance.
      *
-     * @throws NullPointerException If the {@link Context} has not been provided.
      * @throws IllegalStateException If both audio and video have been removed (otherwise the output
      *     would not contain any samples).
      * @throws IllegalStateException If the muxer doesn't support the requested audio MIME type.
      * @throws IllegalStateException If the muxer doesn't support the requested video MIME type.
      */
     public Transformer build() {
-      // TODO(huangdarwin): Remove this checkNotNull after deprecated {@link #setContext(Context)}
-      // is removed.
-      checkNotNull(context);
       if (transformationRequest.audioMimeType != null) {
         checkSampleMimeType(transformationRequest.audioMimeType);
       }