[Checker Framework Upgrade] Suppress warnings emitted by Checker Framework version 2.8.2

More information (LSC)
https://docs.google.com/document/d/16tpK6aXqN68PvTyvt4siM-m7f0NXi_8xEeitLDzr8xY/edit?usp=sharing

Tested:
    tap_presubmit: http://test/OCL:253818309:BASE:253788332:1560879553629:9dc07a48
    Some tests failed; test failures are believed to be unrelated to this CL
PiperOrigin-RevId: 253858263

library/core/src/main/java/com/google/android/exoplayer2/analytics/PlaybackStatsListener.java

@@ -713,6 +713,8 @@ public final class PlaybackStatsListener
      *
      * @param isFinal Whether this is the final build and no further events are expected.
      */
+    // TODO(b/133387873): incompatible types in conditional expression.
+    @SuppressWarnings("nullness:conditional.type.incompatible")
     public PlaybackStats build(boolean isFinal) {
       long[] playbackStateDurationsMs = this.playbackStateDurationsMs;
       List<long[]> mediaTimeHistory = this.mediaTimeHistory;