Remove deprecated readSource method

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=151840862

library/core/src/main/java/com/google/android/exoplayer2/BaseRenderer.java

@@ -255,14 +255,6 @@ public abstract class BaseRenderer implements Renderer, RendererCapabilities {
   }
 
   /**
-   * Use {@link #readSource(FormatHolder, DecoderInputBuffer, boolean)} instead.
-   */
-  @Deprecated
-  protected final int readSource(FormatHolder formatHolder, DecoderInputBuffer buffer) {
-    return readSource(formatHolder, buffer, false);
-  }
-
-  /**
    * Reads from the enabled upstream source. If the upstream source has been read to the end then
    * {@link C#RESULT_BUFFER_READ} is only returned if {@link #setCurrentStreamFinal()} has been
    * called. {@link C#RESULT_NOTHING_READ} is returned otherwise.