Drop isRecording() from core-tracing

[howieleung]

• Package Name: core-tracing
• Package Version:
• Operating system:
• nodejs
  • version:
• browser
  • name/version:
• typescript
  • version:
• Is the bug related to documentation in
  • README.md
  • source code documentation
  • SDK API docs on https://learn.microsoft.com

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Check this comment:
#31160 (comment)

With the current code of otel, there is no reason to check isRecording() and avoid setting attributes, event, status if it is false. It is because otel is checking isEnded inside of these functions and do nothing.

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