fix: correct circle() diameter explanation in Get Started tutorial

[aashu2006]

Summary

This PR fixes an incorrect explanation of the third parameter of the circle() function in the Get Started tutorial.

The tutorial previously stated that a value of 100 results in a circle that is 50 pixels wide and high, which is incorrect.

Changes

• Updated the explanation to correctly describe the third parameter as the diameter.
• Clarified that a diameter of 100 results in a circle that is 100 pixels wide and 100 pixels high.

Related Issue

Resolves #1095

[aashu2006]

Hi there! Just a gentle ping on this PR.
Let me know if there is anything I should update or improve.

[ksen0]

Thank you for working on-fixing this issue, we reviewed the fix and it looks good to go, I'll go ahead and merge it! We would like to note that after an issue is created, we review the issues and assign them to specific contributors (usually as “first come, first serve”). In the future, please wait to be assigned to an issue before opening a PR to fix it. You can reference the Contributors Guidelines

[aashu2006]

Thank you for the review and for merging this! I appreciate the note as well, I will make sure to wait for assignment before opening PRs in the future. Thanks again for the guidance and for taking the time to review 🙂