Add term entry for Single Inheritance in Python

[Prankisster]

Description

This pull request adds a new term entry titled "Single Inheritance" under the path:
content/python/concepts/inheritance/terms/single-inheritance/single-inheritance.md

The entry includes:

• A clear and concise definition of single inheritance in Python
• A diagram illustrating the concept
• A ## Syntax section with usage format
• An ## Example with real-world context
• A ## Codebyte section with runnable Python code
• Proper metadata, subjects, tags, and catalog content
• Compliance with Codecademy’s content, markdown, and style guidelines

Issue Solved

Closes #7078

Type of Change

• Adding a new entry
• Editing an existing entry (fixing a typo, bug, issues, etc)
• Updating the documentation

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.

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