chore(llmobs): fix root span tag for telemetry metrics

[Yun-Kim]

Fixes an incorrect boolean check for if a llmobs span is a root span for LLMObs telemetry metrics. This is not user facing.

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions]

CODEOWNERS have been resolved as:

ddtrace/llmobs/_telemetry.py                                            @DataDog/ml-observability

[github-actions]

Bootstrap import analysis

Comparison of import times between this PR and main.

Summary

The average import time in this PR is: 237 ± 2 ms.

The average import time in main is: 239 ± 2 ms.

The import time difference between this PR and main is: -1.8 ± 0.09 ms.

Import time breakdown

The following import paths have grown:

ddtrace.auto 0.019 ms (0.01%)

ddtrace.bootstrap.sitecustomize 0.019 ms (0.01%)

ddtrace.bootstrap.preload 0.019 ms (0.01%)

ddtrace.internal.products 0.019 ms (0.01%)

ddtrace.settings.dynamic_instrumentation 0.019 ms (0.01%)

The following import paths have shrunk:

ddtrace.auto 1.926 ms (0.81%)

ddtrace.bootstrap.sitecustomize 1.278 ms (0.54%)

ddtrace.bootstrap.preload 1.278 ms (0.54%)

ddtrace.internal.products 1.278 ms (0.54%)

ddtrace.internal.remoteconfig.client 0.633 ms (0.27%)

ddtrace 0.648 ms (0.27%)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-03-20 21:33:22

Comparing candidate commit bdfc241 in PR branch yunkim/llmobs-root-span-telemetry with baseline commit c314bed in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 498 metrics, 2 unstable metrics.