Bump sshkit from 1.17.0 to 1.21.0

[dependabot-preview]

Bumps sshkit from 1.17.0 to 1.21.0.

Release notes

Sourced from sshkit's releases.

1.21.0

✨ New Features

• Allow a Proc to be used as an interaction_handler (#436) @DamienRobert

📚 Documentation

• Removed dead links from README (#477) @ssimontis

🏠 Housekeeping

• Unpin mocha version and fix deprecation warnings for mocha v1.11.1 (#480) @floehopper
• Pin mocha at 1.9.x to fix CI failures (#478) @mattbrictson
• Add changelog_uri to metadata to easily link from rubygems.org (#473) @nickhammond
• Automatically maintain release notes using GitHub Actions (#472) @mattbrictson

1.20.0

• #468: Make upload! take a :verbosity option like exec does - @grosser

1.19.1

• #465: Fix a regression in 1.19.0 that prevented ~ from being used in Capistrano paths, e.g. :deploy_to, etc. - @grosser

1.19.0

• #455: Ensure UUID of commands are stable in logging - @lazyatom
• #453: as and within now properly escape their user/group/path arguments, and the command nested within an as block is now properly escaped before passing to sh -c. In the unlikely case that you were manually escaping commands passed to SSHKit as a workaround, you will no longer need to do this. See #458 for examples of what has been fixed. - @grosser
• #460: Handle IPv6 addresses without port - @will-in-wi

1.18.2

• #448: Fix misbehaving connection eviction loop when disabling connection pooling - Sebastian Cohnen

1.18.1

• #447: Fix broken thread safety by widening critical section - Takumasa Ochi

1.18.0

• #435: Consistent verbosity configuration #capture and #test methods - @NikolayRys

Commits

• a4ad4b6 Release 1.21.1
• 810651d Command: wrap a Proc interaction_handler into a MappingInteractionHandler (#436)
• d69522c Unpin mocha version and fix deprecation warnings for mocha v1.11.1 (#480)
• 9166ea4 Pin mocha at 1.9.x to fix CI failures (#478)
• af9cefd Removed dead links from README (#477)
• d5a3e63 Add changelog_uri to metadata to easily link from rubygems.org (#473)
• 986331e Merge pull request #472 from capistrano/chores/use-github-actions-for-releases
• b245b18 Automatically maintain release notes w/ GH Actions
• eb506cb Preparing v1.20.0
• 6e069d7 Merge pull request #468 from grosser/grosser/silence
• Additional commits viewable in compare view

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