chore: remove deprecated DSA support

[lkingland]

Fixes:

> make check
pkg/ssh/ssh_dialer.go:347:4: SA1019: ssh.KeyAlgoDSA is deprecated: DSA is only supported at insecure key sizes, and was removed from major implementations. (staticcheck)
                        ssh.KeyAlgoDSA,
                        ^

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.73%. Comparing base (211df16) to head (c86c1dd).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2941      +/-   ##
==========================================
+ Coverage   59.97%   60.73%   +0.76%     
==========================================
  Files         130      132       +2     
  Lines       16626    16625       -1     
==========================================
+ Hits         9971    10098     +127     
+ Misses       5728     5572     -156     
- Partials      927      955      +28     

Flag	Coverage Δ
e2e-tests	41.76% <ø> (+1.37%)	⬆️
integration-tests	55.38% <ø> (+1.70%)	⬆️
unit-tests	47.47% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[gauron99]

/lgtm
/approve

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gauron99, lkingland

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [gauron99,lkingland]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment