Bump urllib3 from 1.26.1 to 1.26.3

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.1 to 1.26.3.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@1.26.1...1.26.3)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -90,7 +90,7 @@ terminado==0.9.1
 testpath==0.4.4
 tornado==6.1
 traitlets==5.0.5
-urllib3==1.26.1
+urllib3==1.26.3
 wcwidth==0.2.5
 webencodings==0.5.1
 widgetsnbextension==3.5.1