Change command to install Git in Termux

[nukhes]

Why:

Closes: #39217

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

Change apt install git to pkg install git.

Termux recommends using pkg instead of apt directly, pkg is a wrapper that performs useful tasks:

• Provides command shortcuts.
• Automatically runs "apt update" before installing a package.
• Performs some client side repository load-balancing by automatically switching mirrors.

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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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
get-started/git-basics/set-up-git.md	fpt ghec ghes@ 3.17 3.16 3.15 3.14 3.13	fpt ghec ghes@ 3.17 3.16 3.15 3.14 3.13

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

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[Sharra-writes]

Thanks for opening an issue and PR! This appears to be correct, so I'll go ahead and get the PR merged once checks are passing.

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