Update flask-migrate requirement from ~=2.5.3 to ~=2.7.0

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@v2.5.3...v2.7.0)

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

Author: dependabot[bot]

requirements.txt

@@ -3,7 +3,7 @@ ddtrace
 Flask~=1.1.2
 Flask-Gzip~=0.2
 Flask-Mail~=0.9.1
-Flask-Migrate~=2.5.3
+Flask-Migrate~=2.7.0
 Flask-pyoidc~=3.7.0
 flask_sqlalchemy~=2.4.4
 gunicorn~=20.0.4