fix(sdk-metrics): remove invalid default value for 'startTime' param to ExponentialHistogramAccumulation

[trentm]

Fixes: #5755

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.01%. Comparing base (019cb2c) to head (737c14a).
Report is 22 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5763      +/-   ##
==========================================
- Coverage   95.03%   95.01%   -0.03%     
==========================================
  Files         310      303       -7     
  Lines        7998     7957      -41     
  Branches     1615     1609       -6     
==========================================
- Hits         7601     7560      -41     
  Misses        397      397              

Files with missing lines	Coverage Δ
...sdk-metrics/src/aggregator/ExponentialHistogram.ts	98.16% <100.00%> (ø)

... and 17 files with indirect coverage changes

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[trentm]

FWIW, none of the other *Accumulation constructors set a default value for the startTime param:

% cd opentelemetry-js/packages/sdk-metrics/src

% rg public\ startTime:\ HrTime
aggregator/Histogram.ts
68:    public startTime: HrTime,

aggregator/ExponentialHistogram.ts
68:    public startTime: HrTime = startTime,

aggregator/Sum.ts
32:    public startTime: HrTime,

aggregator/LastValue.ts
33:    public startTime: HrTime,

[pichlermarc]

thanks! 🙂