Fix documentation super-nit.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=118924198

library/src/main/java/com/google/android/exoplayer/dash/DashChunkSource.java

@@ -394,7 +394,7 @@ public class DashChunkSource implements ChunkSource {
         // The previous chunk was from a period that's no longer on the manifest, therefore the
         // The previous chunk was from a period that's no longer on the manifest, therefore the
         // next chunk must be the first one in the first period that's still on the manifest
         // next chunk must be the first one in the first period that's still on the manifest
         // (note that we can't actually update the segmentNum yet because the new period might
         // (note that we can't actually update the segmentNum yet because the new period might
-        // have a different sequence and it's segmentIndex might not have been loaded yet).
+        // have a different sequence and its segmentIndex might not have been loaded yet).
         periodHolder = periodHolders.valueAt(0);
         periodHolder = periodHolders.valueAt(0);
         startingNewPeriod = true;
         startingNewPeriod = true;
       } else if (!periodHolder.isIndexUnbounded()) {
       } else if (!periodHolder.isIndexUnbounded()) {