[receiverhelper] Update metric units

[crobert-1]

Description

1 isn't an informative unit for metrics, this should clarify their units.

Link to tracking issue

Fixes #10650

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.38%. Comparing base (43ed618) to head (c610c3c).
Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10657      +/-   ##
==========================================
+ Coverage   92.32%   92.38%   +0.06%     
==========================================
  Files         397      403       +6     
  Lines       18701    18729      +28     
==========================================
+ Hits        17265    17303      +38     
+ Misses       1076     1066      -10     
  Partials      360      360              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[codeboten]

Thanks @crobert-1