Bump flask from 3.0.0 to 3.0.3 in /stix_shifter

Bumps [flask](https:/pallets/flask) from 3.0.0 to 3.0.3.
- [Release notes](https:/pallets/flask/releases)
- [Changelog](https:/pallets/flask/blob/main/CHANGES.rst)
- [Commits](pallets/flask@3.0.0...3.0.3)

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

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

stix_shifter/requirements.txt

@@ -7,7 +7,7 @@ asynctest==0.13.0
 attrs==23.1.0
 azure-identity==1.15.0
 colorlog==6.8.2
-flask==3.0.0
+flask==3.0.3
 flatten_json==0.1.14
 json-fix==1.0.0
 jsonmerge==1.9.2