Clarifying that GITHUB_TOKEN can be used to install packages from other private repositories

[jlawrence]

Why:

Prevents a misunderstanding that GITHUB_TOKEN cannot be used to install packages from other private repositories.

Closes: #35922

What's being changed:

Updated a phrase concerning GITHUB_TOKEN with new wording and a link to the page that explains how to configure permissions so that GITHUB_TOKEN can be used.

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 a 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 preview environment.

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Content directory changes

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Source	Preview	Production	What Changed
packages/learn-github-packages/introduction-to-github-packages.md	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	from reusable
packages/working-with-a-github-packages-registry/working-with-the-apache-maven-registry.md	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	from reusable
packages/working-with-a-github-packages-registry/working-with-the-container-registry.md	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	from reusable
packages/working-with-a-github-packages-registry/working-with-the-docker-registry.md	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	from reusable
packages/working-with-a-github-packages-registry/working-with-the-gradle-registry.md	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	from reusable
packages/working-with-a-github-packages-registry/working-with-the-npm-registry.md	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	from reusable
packages/working-with-a-github-packages-registry/working-with-the-nuget-registry.md	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	from reusable
packages/working-with-a-github-packages-registry/working-with-the-rubygems-registry.md	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	fpt ghec ghes@ 3.15 3.14 3.13 3.12 3.11 3.10	from reusable

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

[nguyenalex836]

@jlawrence Thanks so much for opening a PR with this fix! I'll update the branch and get this merged once tests are passing 🍏

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