Update dependency Django to v3.1.5

[renovate[bot]]

This PR contains the following updates:

Package	Update	Change
Django (source, changelog)	patch	==3.1.2 -> ==3.1.5

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Release Notes

django/django

### [`v3.1.5`](https://togithub.com/django/django/compare/3.1.4...3.1.5) [Compare Source](https://togithub.com/django/django/compare/3.1.4...3.1.5) ### [`v3.1.4`](https://togithub.com/django/django/compare/3.1.3...3.1.4) [Compare Source](https://togithub.com/django/django/compare/3.1.3...3.1.4) ### [`v3.1.3`](https://togithub.com/django/django/compare/3.1.2...3.1.3) [Compare Source](https://togithub.com/django/django/compare/3.1.2...3.1.3)

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