Add documentation for Python binascii.a2b_hex() method

[Tia-ani]

This PR adds a new entry for the a2b_base16() function under Python's binascii module concepts.

The documentation includes:

• Method description and functionality
• Syntax with parameters, return values, and exceptions
• Practical example showing hexadecimal to binary conversion
• Interactive codebyte demonstrating various use cases

File added: content/python/concepts/binascii-module/terms/a2b-base16/a2b-base16.md

• Solved issue [Term Entry] Python binascii-module: .a2b_hex() #7698
• Closes [Term Entry] Python binascii-module: .a2b_hex() #7698

[mamtawardhani]

Looks good for a second review! 🚀

[Radhika-okhade]

Made slight change to the description.
The entry looks good to be merged.

[github-actions]

👋 @Tia-ani
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!

🎉 Your contribution(s) can be seen here:

https://www.codecademy.com/resources/docs/python/binascii-module/a2b-hex

Please note it may take a little while for changes to become visible.
If you're appearing as anonymous and want to be credited, visit the linked accounts page and ensure that your GitHub account is linked.