chore: upgrade signalflow-client-go to v2

[chimanjain]

Upgrade SignalFx SignalFlow client dependency github.com/signalfx/signalflow-client-go to v2.

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 29.86%. Comparing base (61582f7) to head (5efd09e).
⚠️ Report is 17 commits behind head on main.
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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1936      +/-   ##
==========================================
- Coverage   30.00%   29.86%   -0.14%     
==========================================
  Files         288      288              
  Lines       18455    18614     +159     
==========================================
+ Hits         5537     5560      +23     
- Misses      12189    12325     +136     
  Partials      729      729              

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