fix: Add a small fudge to prefetch eviction (#8470)

This will prevent duplicate segments from being downloaded when we are
close to the live edge.

Author: avelad

lib/media/streaming_engine.js

@@ -1562,7 +1562,10 @@ shaka.media.StreamingEngine = class {
 
     if (mediaState.segmentPrefetch && mediaState.segmentIterator &&
         !this.audioPrefetchMap_.has(mediaState.stream)) {
-      mediaState.segmentPrefetch.evict(reference.startTime);
+      // This will prevent duplicate segments from being downloaded when we
+      // are close to the live edge.
+      const fudgeTime = 0.001;
+      mediaState.segmentPrefetch.evict(reference.startTime + fudgeTime);
       mediaState.segmentPrefetch.prefetchSegmentsByTime(reference.startTime)
           // We're treating this call as sync here, so ignore async errors
           // to not propagate them further.