Update dependency social-auth-app-django to v4

[renovate]

This PR contains the following updates:

Package	Update	Change
social-auth-app-django	major	==3.1.0 -> ==4.0.0

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Release Notes

python-social-auth/social-app-django

v4.0.0

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Changed

• Dropped support for older Django versions (1.8, 1.9, 1.10, 2.0)
• Fix TypeError when continuing a pipeline in Django 2.1

v3.4.0

Compare Source

Changed

• Correct release mechanism

v3.3.0

Compare Source

Changed

• Updated release and tests mechanism

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