Doc update to use my-sample-project as example repository

What does this MR do?

1. Switched from project.git to my-sample-project.git for example commands.
2. Added cd my-sample-project as new text, so that we you issue git lfs init you are in the correct dir

Using my-sample-project.git due to https://docs.gitlab.com/ee/tutorials/make_your_first_git_commit.html

Related issues

Author's checklist

• Optional. Consider taking the GitLab Technical Writing Fundamentals course.
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If you are a GitLab team member and only adding documentation, do not add any of the following labels:

• ~"frontend"
• ~"backend"
• ~"type::bug"
• ~"database"

These labels cause the MR to be added to code verification QA issues.

Reviewer's checklist

Documentation-related MRs should be reviewed by a Technical Writer for a non-blocking review, based on Documentation Guidelines and the Style Guide.

• If the content requires it, ensure the information is reviewed by a subject matter expert.
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    • The headings should be something you'd do a Google search for. Instead of Default behavior, say something like Default behavior when you close an issue.
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