Bump flask-migrate from 2.4.0 to 2.5.2

Bumps [flask-migrate](https://github.com/miguelgrinberg/flask-migrate) from 2.4.0 to 2.5.2.
- [Release notes](https://github.com/miguelgrinberg/flask-migrate/releases)
- [Changelog](https://github.com/miguelgrinberg/Flask-Migrate/blob/master/CHANGES.md)
- [Commits](https://github.com/miguelgrinberg/flask-migrate/compare/v2.4.0...v2.5.2)

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

setup.py

@@ -34,7 +34,7 @@ setup(
     install_requires=[
         'Flask==1.0.3',
         'flask-sqlalchemy==2.4.0',
-        'Flask-Migrate==2.4.0',
+        'Flask-Migrate==2.5.2',
         'flask-bootstrap==3.3.7.1',
         'flask-nav==0.6',
         'flask-wtf==0.14.2',