Update flasgger requirement from ~=0.9.4 to ~=0.9.7 in /frontend

Updates the requirements on [flasgger](https://github.com/flasgger/flasgger) to permit the latest version.
- [Release notes](https://github.com/flasgger/flasgger/releases)
- [Changelog](https://github.com/flasgger/flasgger/blob/master/HISTORY)
- [Commits](flasgger/flasgger@0.9.4...v0.9.7.1)

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

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

frontend/requirements.txt

@@ -1,5 +1,5 @@
 flask~=2.0
-flasgger~=0.9.4
+flasgger~=0.9.7
 flask_restful~=0.3.7
 elasticsearch~=7.0
 spacy~=2.2