Bump sentencepiece from 0.2.0 to 0.2.1 in /examples/video-comprehension (#2377)

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Author: dependabot[bot]

examples/video-comprehension/requirements.txt

@@ -1,2 +1,2 @@
 av == 12.1.0
-sentencepiece == 0.2.0
+sentencepiece == 0.2.1