Add MOD() term entry under SQL math-functions with syntax and examples

[Bprs68]

Description

Added a new term entry for the SQL math function MOD() under content/sql/concepts/math-functions/terms/mod/mod.md.
This entry introduces the MOD() function, provides syntax, and includes examples demonstrating its use in SQL.
The motivation is to expand documentation on SQL math functions and address the need for a clear explanation of MOD() for users.

Issue Solved

Closes #7533

Type of Change

• Adding a new entry

Checklist

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

[CLAassistant]

All committers have signed the CLA.

[mamtawardhani]

Looks good for a second review! 🚀