fix(ci): pin idna_adapter to 1.2.1

[oleonardolima]

Description

It fixes the MSRV CI by pining idna_adapter.

Notes to the reviewers

I noticed it's broken after merging #441, this PR should fix it.

Changelog notice

### Changed
- fix(ci): pin `idna_adapter` to `1.2.1`

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran just p before pushing

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.21%. Comparing base (6ec0146) to head (d3fe261).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #466   +/-   ##
=======================================
  Coverage   80.21%   80.21%           
=======================================
  Files          24       24           
  Lines        5348     5348           
  Branches      242      242           
=======================================
  Hits         4290     4290           
  Misses        980      980           
  Partials       78       78           

Flag	Coverage Δ
rust	80.21% <ø> (ø)

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.

[luisschwab]

ACK d3fe261