Update dependency sinatra to v4

[renovate]

This PR contains the following updates:

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

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Release Notes

sinatra/sinatra (sinatra)

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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[renovate]

⚠️ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
• the branch becomes conflicted, or
• you click the rebase/retry checkbox if found above, or
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The artifact failure details are included below:

File name: Gemfile.lock

Fetching gem metadata from https://rubygems.org/.........
Resolving dependencies...

Could not find compatible versions

Because sinatra >= 4.0.0 depends on rack >= 3.0.0, < 4
  and Gemfile depends on rack = 2.2.9,
  sinatra >= 4.0.0 cannot be used.
So, because Gemfile depends on sinatra = 4.0.0,
  version solving has failed.