testbed: use fluent assertThat and remove stale nanos TODO

[fossadvocate86]

Two TestUtils.assertSameTrace() methods in the sdk/trace and opentracing-shim
testbeds carry a TODO - Include nanos in this comparison. that has been stale since
the API was migrated to return epoch nanoseconds directly via getEndEpochNanos().

sdk/trace testbed

Replace assertThat(a >= b).isTrue() with assertThat(a).isGreaterThanOrEqualTo(b)
and remove the TODO comment.

The old form fails with expected: true, but was: false — no diagnostic information.
The new fluent form reports the actual nanosecond values on failure, making it
immediately actionable.

opentracing-shim testbed

Already used the fluent form (.isLessThanOrEqualTo). Remove the now-stale TODO
comment.

Testing

• LateSpanFinishTest (sdk/trace) — the sole caller of the sdk/trace version ✅
• LateSpanFinishTest (opentracing-shim) ✅
• OpenTelemetryInteroperabilityTest (opentracing-shim) — 2 tests that call assertSameTrace ✅

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: fossadvocate86 / name: fossadvocate86 (7762b98)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.63%. Comparing base (c12e11b) to head (6d0c9c5).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8607   +/-   ##
=========================================
  Coverage     91.63%   91.63%           
- Complexity    10326    10327    +1     
=========================================
  Files          1013     1013           
  Lines         27295    27295           
  Branches       3205     3205           
=========================================
+ Hits          25011    25012    +1     
  Misses         1558     1558           
+ Partials        726      725    -1     

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[fossadvocate86]

/easycla

[otelbot]

Thank you for your contribution @fossadvocate86! 🎉 We would like to hear from you about your experience contributing to OpenTelemetry by taking a few minutes to fill out this survey.