Bump idna from 3.4 to 3.7 in /examples/dataflow-flex-python (#1257)

Bumps [idna](https://github.com/kjd/idna) from 3.4 to 3.7.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.rst)
- [Commits](kjd/idna@v3.4...v3.7)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Andrew Gold <41129777+agold-rh@users.noreply.github.com>

examples/dataflow-flex-python/requirements.txt

@@ -55,7 +55,7 @@ grpcio-gcp==0.2.2
 grpcio-status==1.48.2
 hdfs==2.7.0
 httplib2==0.20.4
-idna==3.4
+idna==3.7
 numpy==1.22.4
 oauth2client==4.1.3
 orjson==3.9.15