docs: clarify fork-and-pull model wording (replace 'of it' with 'that')

[krsnaSuraj]

Why:

Closes: #44811

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

Replaces the clunky phrase "a fork of it you created" with "a fork that you created" in the "Fork and pull model" section of content/pull-requests/collaborating-with-pull-requests/getting-started/about-collaborative-development-models.md. This is a grammatical/clarity correction (no technical meaning changed), which the docs team explicitly accepts and a maintainer pre-approved in the linked issue.

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.

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Source	Review	Production	What Changed
pull-requests/collaborating-with-pull-requests/getting-started/about-collaborative-development-models.md	fpt ghec ghes@ 3.21 3.20 3.19 3.18 3.17	fpt ghec ghes@ 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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[Copilot]

Pull request overview

This PR makes a small clarity/grammar improvement in the “Fork and pull model” section by replacing the phrase “a fork of it you created” with the clearer “a fork that you created,” without changing the technical meaning.

Changes:

• Updates one sentence in the fork-and-pull model description to remove awkward wording.