Update dependency sphinx to v3

This MR contains the following updates:

Package	Type	Update	Change
sphinx	dev-dependencies	major	^2.1 -> ^3.0

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This MR has been generated by Renovate Bot.

added 4 commits

• b3d7ed8a...303788ab - 3 commits from branch master
• 85ef1233 - Update dependency sphinx to v3

Compare with previous version

marked the checklist item If you want to rebase/retry this MR, check this box as completed

added 10 commits

• 85ef1233...4f7daeb6 - 9 commits from branch master
• c9df7fbd - Merge branch 'master' into 'renovate/sphinx-3.x'

Compare with previous version

mentioned in commit ab5bfc66

merged