Revert "Enable OTel metrics by default (#2859)"

[kislaykishore]

This reverts commit 94c5ebd.

Description

• This is causing some of the periodic tests to fail. These tests fetch the metrics using certain attributes that are valid only in the opencensus world. At the moment, I don't have bandwidth to check this. So, reverting it.

Link to the issue in case of a bug fix.

b/387898221

Testing details

1. Manual - NA
2. Unit tests - NA
3. Integration tests - NA

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.22%. Comparing base (440fce6) to head (11f5461).
Report is 7 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2882      +/-   ##
==========================================
+ Coverage   76.11%   76.22%   +0.11%     
==========================================
  Files         118      118              
  Lines       16600    16637      +37     
==========================================
+ Hits        12635    12682      +47     
+ Misses       3431     3424       -7     
+ Partials      534      531       -3     

Flag	Coverage Δ
unittests	76.22% <100.00%> (+0.11%)	⬆️

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