Update flask-sqlalchemy to 2.5.1

[pyup-bot]

This PR updates Flask-SQLAlchemy from 2.4.4 to 2.5.1.

Changelog

2.5.1

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Released 2021-03-18

-   Fix compatibility with Python 2.7.

2.5.0

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Released 2021-03-18

-   Update to support SQLAlchemy 1.4.
-   SQLAlchemy ``URL`` objects are immutable. Some internal methods have
 changed to return a new URL instead of ``None``. :issue:`885`

Links

• PyPI: https://pypi.org/project/flask-sqlalchemy
• Changelog: https://pyup.io/changelogs/flask-sqlalchemy/
• Repo: https://github.com/pallets/flask-sqlalchemy
• Docs: https://pythonhosted.org/Flask-SQLAlchemy/

[coveralls]

Coverage remained the same at 86.667% when pulling d36dc62 on pyup-update-flask-sqlalchemy-2.4.4-to-2.5.1 into b73c34e on master.