test(shim-opentracing): add comparison thresholds in flaky assertions

[cjihrig]

Which problem is this PR solving?

These equality assertions can be flaky due to floating point math.

Fixes: https://github.com/open-telemetry/opentelemetry-js/actions/runs/18082260606/job/51447397928?pr=5962

Short description of the changes

This commit updates the assertions to allow a small threshold.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Existing test suite

Checklist:

• Followed the style guidelines of this project

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.17%. Comparing base (09bf31e) to head (4c6d26b).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@ ## main #5974 +/- ## ======================================= Coverage 95.17% 95.17% ======================================= Files 316 316 Lines 8521 8521 Branches 1763 1763 ======================================= Hits 8110 8110 Misses 411 411 

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[pichlermarc]

thanks! 🙂

[otelbot]

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