Fix typo in gallery example (#6276)

Co-authored-by: Alexander Jipa <azzhipa@amazon.com>

gallery/plot_video_api.py

@@ -170,7 +170,7 @@ vf, af, info, meta = example_read_video(video)
 print(vf.size(), af.size())
 
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-# 3. Building an example randomly sampled dataset (can be applied to training dataest of kinetics400)
+# 3. Building an example randomly sampled dataset (can be applied to training dataset of kinetics400)
 # -------------------------------------------------------------------------------------------------------
 # Cool, so now we can use the same principle to make the sample dataset.
 # We suggest trying out iterable dataset for this purpose.