build(deps): bump flask from 1.1.2 to 2.3.2 in /src

Bumps [flask](https://github.com/pallets/flask) from 1.1.2 to 2.3.2.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/main/CHANGES.rst)
- [Commits](https://github.com/pallets/flask/compare/1.1.2...2.3.2)

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

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

src/requirements.txt

@@ -1,5 +1,5 @@
 Markdown==3.1.1
 WTForms==2.2.1
-Flask==1.1.2
+Flask==2.3.2
 Flask_WTF==0.14.3
 Whoosh==2.7.4