docs: Update OpenTelemetry section in README.rst

[nickmarx12345678]

Move instructions off deprecated module.

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> 🦕

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[Linchin]

Hi @nickmarx12345678, thank you for contributing to this repo! Please sign the cla agreement, it's legally required to make code changes.

[nickmarx12345678]

Done!

…

On Tue, Dec 5, 2023 at 9:57 AM Lingqing Gan ***@***.***> wrote: Hi @nickmarx12345678 <https://github.com/nickmarx12345678>, thank you for contributing to this repo! Please sign the cla agreement <https://github.com/googleapis/python-bigquery/pull/1743/checks?check_run_id=19302898945>, it's legally required to make code changes. — Reply to this email directly, view it on GitHub <#1743 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAROFMIDJ33X42LIRMHYP4LYH5N7XAVCNFSM6AAAAABAGSJSMCVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTQNBRGMZDKNRWGM> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[chalmerlowe]

LGTM