Clarify telemetry opt-out values

[sanzanazaman]

Why:

The current wording does not make clear that DO_NOT_TRACK accepts only true or 1.
Closes: #45957

What's being changed (if available, include any code snippets, screenshots, or gifs):

Clarifies the documented opt-out values for GH_TELEMETRY and DO_NOT_TRACK in the GitHub CLI telemetry article. The values were checked against the GitHub CLI environment variable reference.

Check off the following:

• A subject matter expert (SME) has reviewed the technical accuracy of the content in this PR. In most cases, the author can be the SME. Open source contributions may require an SME review from GitHub staff.
• The changes in this PR meet the docs fundamentals that are required for all content.
• All CI checks are passing and the changes look good in the review environment.

[github-actions]

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Source	Review	Production	What Changed
github-cli/github-cli/github-cli-telemetry.md	fpt ghec ghes@ 3.22 3.21 3.20 3.19 3.18 3.17	fpt ghec ghes@ 3.22 3.21 3.20 3.19 3.18 3.17

Key: fpt: Free, Pro, Team; ghec: GitHub Enterprise Cloud; ghes: GitHub Enterprise Server

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[UmeshCode1]

This is a great clarification.

The previous phrasing ("Any falsy value works: 0, false, disabled, or an empty string. You can also use the DO_NOT_TRACK convention:") could easily mislead users into assuming DO_NOT_TRACK also required a falsy value to opt out, when in fact the DO_NOT_TRACK=1 / true console standard requires a truthy value to disable tracking.

Explicitly delineating the active opt-out values for both environment variables (GH_TELEMETRY falsy vs DO_NOT_TRACK truthy) resolves that ambiguity cleanly. Content linters and Playwright test suite are green. LGTM!

[subatoi]

As I noted here, we're not accepting contributions for this at this time, so I'm going to close this out

[sanzanazaman]

Thanks for clarifying!