Typo in telemetry logs disablement scenario env var

[eliottness]

Changes

This PR fixes a typo I found while enabling some system-tests about telemetry following the instrumentation telemetry client full revamp in dd-trace-go. Here are the places that mention the env var without a S:

• The instrumentation telemetry api docs: https://github.com/DataDog/instrumentation-telemetry-api-docs/blob/main/GeneratedDocumentation/ApiDocs/v2/development.md#telemetry-environment-variables
• dd-trace-rb docs: https://datadoghq.dev/dd-trace-rb/Datadog/Core/Configuration/Settings/DSL/Telemetry.html
• dd-trace-js config: https://github.com/DataDog/dd-trace-js/blob/fd425151b56f41cc71a2b39ba088b72491283ae8/packages/dd-trace/test/config.spec.js#L1729

Why this did not fail before ?

No tracer has the only test running in this scenario enabled.

Workflow

1. ⚠️ Create your PR as draft ⚠️
2. Work on you PR until the CI passes (if something not related to your task is failing, you can ignore it)
3. Mark it as ready for review
   • Test logic is modified? -> Get a review from RFC owner. We're working on refining the codeowners file quickly.
   • Framework is modified, or non obvious usage of it -> get a review from R&P team

🚀 Once your PR is reviewed, you can merge it!

🛟 #apm-shared-testing 🛟

Reviewer checklist

• If PR title starts with [<language>], double-check that only <language> is impacted by the change
• No system-tests internal is modified. Otherwise, I have the approval from R&P team
• CI is green, or failing jobs are not related to this change (and you are 100% sure about this statement)
• A docker base image is modified?
  • the relevant build-XXX-image label is present
• A scenario is added (or removed)?
  • Get a review from R&P team