demo: remove copy referring to telemetry disabling env var

[angles-n-daemons]

demo: remove copy referring to telemetry disabling env var

COCKROACH_SKIP_ENABLING_DIAGNOSTIC_REPORTING can still be used to disable telemetry for CRDB. With the core deprecation happening however, we want to streamline how people enable / disable telemetry in their cluster, so the copy to this variable has been removed.

It will still function as before, the only difference is that it will not show up in the demo startup message.

Epic: CRDB-40209
Fixes: #132688
Release note (general change):
COCKROACH_SKIP_ENABLING_DIAGNOSTIC_REPORTING is no longer mentioned in the demo command.

[cockroach-teamcity]

This change is 

[angles-n-daemons]

bors r+

[craig]

Build succeeded:

• acceptance
• macos_amd64_build
• macos_arm64_build
• lint
• windows_build
• examples_orms
• linux_amd64_build
• local_roachtest
• docker_image_amd64
• linux_amd64_fips_build
• local_roachtest_fips
• unit_tests
• linux_arm64_build
• check_generated_code

[blathers-crl]

Based on the specified backports for this PR, I applied new labels to the following linked issue(s). Please adjust the labels as needed to match the branches actually affected by the issue(s), including adding any known older branches.

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Issue #132688: branch-release-23.1, branch-release-23.2, branch-release-24.1, branch-release-24.2, branch-release-24.3.

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[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

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error setting reviewers, but backport branch blathers/backport-release-23.1-133284 is ready: POST https://api.github.com/repos/cockroachdb/cockroach/pulls/134083/requested_reviewers: 422 Reviews may only be requested from collaborators. One or more of the teams you specified is not a collaborator of the cockroachdb/cockroach repository. []

Backport to branch 23.1.x failed. See errors above.

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error setting reviewers, but backport branch blathers/backport-release-23.2-133284 is ready: POST https://api.github.com/repos/cockroachdb/cockroach/pulls/134085/requested_reviewers: 422 Reviews may only be requested from collaborators. One or more of the teams you specified is not a collaborator of the cockroachdb/cockroach repository. []

Backport to branch 23.2.x failed. See errors above.

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error setting reviewers, but backport branch blathers/backport-release-24.1-133284 is ready: POST https://api.github.com/repos/cockroachdb/cockroach/pulls/134087/requested_reviewers: 422 Reviews may only be requested from collaborators. One or more of the teams you specified is not a collaborator of the cockroachdb/cockroach repository. []

Backport to branch 24.1.x failed. See errors above.

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error setting reviewers, but backport branch blathers/backport-release-24.2-133284 is ready: POST https://api.github.com/repos/cockroachdb/cockroach/pulls/134088/requested_reviewers: 422 Reviews may only be requested from collaborators. One or more of the teams you specified is not a collaborator of the cockroachdb/cockroach repository. []

Backport to branch 24.2.x failed. See errors above.

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error setting reviewers, but backport branch blathers/backport-release-24.3-133284 is ready: POST https://api.github.com/repos/cockroachdb/cockroach/pulls/134089/requested_reviewers: 422 Reviews may only be requested from collaborators. One or more of the teams you specified is not a collaborator of the cockroachdb/cockroach repository. []

Backport to branch 24.3.x failed. See errors above.

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