build(deps): bump craft-providers to 1.21.0

[mr-cal]

• Have you followed the guidelines for contributing?
• Have you signed the CLA?
• Have you successfully run tox run -m lint?
• Have you successfully run tox run -e test-py310? (supported versions: py39, py310, py311, py312)

---

Bumping craft-providers as a prerequisite for #4519

Changelog

1.21.0 (2024-01-17)

• Update base compatibility tag to base-v6
• Add Ubuntu 24.04 (Noble) support
• Remove Ubuntu 23.04 (Lunar) support

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9fc449a) 89.20% compared to head (ea47b7a) 89.20%.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4530   +/-   ##
=======================================
  Coverage   89.20%   89.20%           
=======================================
  Files         321      321           
  Lines       21759    21759           
=======================================
+ Hits        19410    19411    +1     
+ Misses       2349     2348    -1     

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