Update out-of-date documentation pages

[rrousselGit]

• [ ] concepts/combining_providers.mdx
• [ ] concepts/modifiers/auto_dispose.mdx
• [ ] concepts/modifiers/family.mdx
• [ ] concepts/provider_lifecycles.mdx
• [ ] concepts/provider_observer.mdx
• [ ] concepts/providers.mdx
• [ ] concepts/reading.mdx
• [ ] concepts/scopes.mdx
• [ ] concepts/why_immutability.mdx
• [ ] cookbooks/refresh.mdx
• [ ] cookbooks/search_as_we_type.mdx
• [ ] cookbooks/testing.mdx
• [ ] providers/change_notifier_provider.mdx
• [ ] providers/future_provider.mdx
• [ ] providers/notifier_provider.mdx
• [ ] providers/provider.mdx
• [ ] providers/state_notifier_provider.mdx
• [ ] providers/state_provider.mdx
• [ ] providers/stream_provider.mdx