[chore] Mark github.com/signalfx/signalfx-agent module as local

[dmitryax]

Going forward we need to update all the usages of github.com/signalfx/signalfx-agent to github.com/signalfx/splunk-otel-collector/internal/signalfx-agent

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 44.35%. Comparing base (8db19d3) to head (4040706).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6189      +/-   ##
==========================================
- Coverage   44.41%   44.35%   -0.06%     
==========================================
  Files         390      390              
  Lines       26986    26986              
==========================================
- Hits        11985    11969      -16     
- Misses      14158    14171      +13     
- Partials      843      846       +3     

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[crobert-1]

The thought process makes sense to me, LGTM once lint and the rest of CI is passing