chore(deps): update flask-admin requirement from ~=1.5.5 to ~=1… (#6919)

Updates the requirements on [flask-admin](https://github.com/flask-admin/flask-admin) to permit the latest version.
- [Release notes](https://github.com/flask-admin/flask-admin/releases)
- [Changelog](https://github.com/flask-admin/flask-admin/blob/master/doc/changelog.rst)
- [Commits](pallets-eco/flask-admin@v1.5.5...v1.5.6)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

requirements/common.txt

@@ -49,7 +49,7 @@ blinker~=1.4
 envparse~=0.2
 git+https://github.com/fossasia/[email protected]
 wtforms~=2.2
-flask-admin~=1.5.5
+flask-admin~=1.5.6
 google-compute-engine~=2.8
 factory_boy~=2.12
 sentry-sdk[flask]~=0.14