Bump mistune version (#1117)

Author: dependabot[bot]

examples/pytorch/nlp/huggingface_models/common/examples/research_projects/lxmert/requirements.txt

@@ -40,7 +40,7 @@ kiwisolver==1.2.0
 lockfile==0.12.2
 MarkupSafe==1.1.1
 matplotlib==3.3.1
-mistune==0.8.4
+mistune==2.0.3
 msgpack==0.6.2
 nbclient==0.5.0
 nbconvert==6.0.1