tools: bump boto3 from 1.28.15 to 1.28.20 in /midna

Bumps [boto3](https://github.com/boto/boto3) from 1.28.15 to 1.28.20.
- [Release notes](https://github.com/boto/boto3/releases)
- [Changelog](https://github.com/boto/boto3/blob/develop/CHANGELOG.rst)
- [Commits](boto/boto3@1.28.15...1.28.20)

---
updated-dependencies:
- dependency-name: boto3
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

midna/src/requirements.txt

@@ -1,7 +1,7 @@
 django==4.2.3
 mysqlclient==2.2.0
 bcrypt==4.0.1
-boto3==1.28.15
+boto3==1.28.20
 pytest==7.4.0
 pip-audit==2.6.1
 gunicorn==21.2.0