Bump idna from 2.8 to 3.7 in /examples/research_projects/lxmert (#30200)

Bumps [idna](https://github.com/kjd/idna) from 2.8 to 3.7.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.rst)
- [Commits](https://github.com/kjd/idna/compare/v2.8...v3.7)

---
updated-dependencies:
- dependency-name: idna
  dependency-type: direct:production
...

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examples/research_projects/lxmert/requirements.txt

@@ -21,7 +21,7 @@ entrypoints==0.3
 filelock==3.0.12
 future==0.18.3
 html5lib==1.0.1
-idna==2.8
+idna==3.7
 ipaddr==2.2.0
 ipykernel==5.3.4
 ipython