Update dependency sinatra-contrib to v4

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
sinatra-contrib (source)	'3.2.0' -> '4.0.0'

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Release Notes

sinatra/sinatra (sinatra-contrib)

v4.0.0

Compare Source

• New: Add support for Rack 3 (#​1857)

  • Note: you may want to read the Rack 3 Upgrade Guide

• Require Ruby 2.7.8 as minimum Ruby version (#​1993)

• Breaking change: Drop support for Rack 2 (#​1857)

  • Note: when using Sinatra to start the web server, you now need the rackup gem installed

• Breaking change: Remove the IndifferentHash initializer (#​1982)

• Breaking change: Disable session_hijacking protection by default (#​1984)

• Breaking change: Remove Rack::Protection::EncryptedCookie (#​1989)

  • Note: cookies are still encrypted (by [Rack::Session::Cookie][Rack::Session::Cookie])

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[yegor256]

@rultor please, try to merge, since 8 checks have passed

[rultor]

@rultor please, try to merge, since 8 checks have passed

@yegor256 OK, I'll try to merge now. You can check the progress of the merge here

[rultor]

@rultor please, try to merge, since 8 checks have passed

@yegor256 Done! FYI, the full log is here (took me 9min)