Update file watcher to ignore .swx files

[dhurley]

Proposed changes

Update file watcher to ignore .swx files

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• I have run make install-tools and have attached any dependency changes to this pull request
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• If applicable, I have updated any relevant documentation (README.md)
• If applicable, I have tested my cross-platform changes on Ubuntu 22, Redhat 8, SUSE 15 and FreeBSD 13

[netlify]

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🔨 Latest commit	6a3b364
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[codecov-commenter]

Codecov Report

Patch coverage: 20.00% and project coverage change: +0.14% 🎉

Comparison is base (4747879) 66.29% compared to head (6a3b364) 66.43%.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #466      +/-   ##
==========================================
+ Coverage   66.29%   66.43%   +0.14%     
==========================================
  Files         118      118              
  Lines       13391    13395       +4     
==========================================
+ Hits         8877     8899      +22     
+ Misses       3924     3906      -18     
  Partials      590      590              

Files Changed	Coverage Δ
...hub.com/nginx/agent/v2/src/plugins/file_watcher.go	76.81% <20.00%> (-1.55%)	⬇️

... and 1 file with indirect coverage changes

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