Update flask-migrate requirement from ~=2.2.1 to ~=2.5.3 (#232)

Updates the requirements on [flask-migrate](https://github.com/miguelgrinberg/flask-migrate) to permit the latest version.
- [Release notes](https://github.com/miguelgrinberg/flask-migrate/releases)
- [Changelog](https://github.com/miguelgrinberg/Flask-Migrate/blob/master/CHANGES.md)
- [Commits](miguelgrinberg/Flask-Migrate@v2.2.1...v2.5.3)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements.txt

@@ -4,7 +4,7 @@ Flask-Mail~=0.9.1
 Flask-Gzip~=0.2
 flask_sqlalchemy~=2.4.4
 psycopg2-binary~=2.8.6
-Flask-Migrate~=2.2.1
+Flask-Migrate~=2.5.3
 pylint~=2.6.0
 gunicorn~=20.0.4
 csh_ldap~=2.3.1