Added C++ docs for map .upper_bound() with examples

[ozearkhan]

Description

Added documentation for the map::upper_bound() function in C++. This entry includes a clear explanation of how the function works, usage details, and a simple example demonstrating how to use upper_bound() with a map.

Issue Solved

5479

Type of Change

• Adding a new entry

Checklist

• [x] All writings are my own.
• [x] My entry follows the Codecademy Docs style guide.
• [x] My changes generate no new warnings.
• [x] I have performed a self-review of my own writing and code.
• [x] I have checked my entry and corrected any misspellings.
• [x] I have made corresponding changes to the documentation if needed.
• [x] I have confirmed my changes are not being pushed from my forked main branch.
• [x] I have confirmed that I'm pushing from a new branch named after the changes I'm making.
• [x] I have linked any issues that are relevant to this PR in the Issues Solved section.

[cigar-galaxy82]

Hi @ozearkhan thank you for contributing to Codecademy docs, I see that the example section is missing please add an example.

[ozearkhan]

@cigar-galaxy82 will handle this ASAP. In the meantime, could you please add the Hacktoberfest label to this issue?

[github-actions[bot]]

👋 @ozearkhan You have contributed to Codecademy Docs, and we would like to know more about you and your experience. Please take a minute to fill out this four question survey to help us better understand Docs contributions and how we can improve the experience for you and our learners. Thank you for your help!

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https://www.codecademy.com/resources/docs/cpp/maps/upper-bound

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