Make ExtractorsFactory javadoc consistent

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=213248388

library/core/src/main/java/com/google/android/exoplayer2/extractor/ExtractorsFactory.java

@@ -15,14 +15,9 @@
  */
 package com.google.android.exoplayer2.extractor;
 
-/**
- * Factory for arrays of {@link Extractor}s.
- */
+/** Factory for arrays of {@link Extractor} instances. */
 public interface ExtractorsFactory {
 
-  /**
-   * Returns an array of new {@link Extractor} instances.
-   */
+  /** Returns an array of new {@link Extractor} instances. */
   Extractor[] createExtractors();
-
 }