fix: Fedora Sway Atomic should be recognized as FedoraImmutable

[SteveLauC]

Standards checklist:

• The PR title is descriptive.
• I have read CONTRIBUTING.md
• The code compiles (cargo build)
• The code passes rustfmt (cargo fmt)
• The code passes clippy (cargo clippy)
• The code passes tests (cargo test)
• Optional: I have tested the code myself

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What does this PR do

Closes #783

Before this PR, Topgrade recognized Fedora Sway Atomic as a normal Fedora distro, which is not correct, it should be FedoraImmutable.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 6.78%. Comparing base (767f0d9) to head (70e3f98).

❗ Current head 70e3f98 differs from pull request most recent head 488db7f. Consider uploading reports for the commit 488db7f to get more accurate results

Additional details and impacted files

@@           Coverage Diff            @@
##            main    #795      +/-   ##
========================================
- Coverage   6.91%   6.78%   -0.14%     
========================================
  Files         37      37              
  Lines      11645   11824     +179     
========================================
- Hits         805     802       -3     
- Misses     10840   11022     +182     

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