Bump urllib3 from 1.26.9 to 1.26.18 in /Tutorials/flask_blog

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.9 to 1.26.18.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@1.26.9...1.26.18)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Tutorials/flask_blog/requirements.txt

@@ -163,7 +163,7 @@ traitlets==5.3.0
 Twisted==22.4.0
 typing_extensions==4.2.0
 tzdata==2023.3
-urllib3==1.26.9
+urllib3==1.26.18
 uvicorn==0.17.6
 w3lib==1.22.0
 wcwidth==0.2.5