[receiver/signalfx] Remove from default configurations (excluding gateways)

[crobert-1]

Description:

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 43.16%. Comparing base (15602fb) to head (1a70f68).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6837      +/-   ##
==========================================
- Coverage   43.35%   43.16%   -0.19%     
==========================================
  Files         370      370              
  Lines       26104    26104              
==========================================
- Hits        11317    11268      -49     
- Misses      13963    14015      +52     
+ Partials      824      821       -3     

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