Remove examples of composite actions on GitHub

[tnir]

Why:

• Closes: Examples for composite actions are almost dead #43735

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

Remove examples of composite actions on GitHub since they are getting to use less in these repositories. There are no good other examples to replace them with, and they are not necessary to understand the concept of composite actions.

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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Table of review links

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The table shows the files in the content directory that were changed in this pull request. This helps you review your changes on a staging server. Changes to the data directory are not included in this table.

Source	Review	Production	What Changed
actions/tutorials/create-actions/create-a-composite-action.md	fpt ghec ghes@ 3.20 3.19 3.18 3.17 3.16 3.15 3.14	fpt ghec ghes@ 3.20 3.19 3.18 3.17 3.16 3.15 3.14

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

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[Copilot]

Pull request overview

Removes a now-stale “Example composite actions on GitHub” section from the composite actions tutorial, avoiding links to deprecated/archived repositories while keeping the conceptual guidance intact.

Changes:

• Deleted the “Example composite actions on {% data variables.product.github %}” section.
• Removed three external repository links that have become archived/deprecated.