add popleft() entry

[LasVegas98]

##Description

Added a new entry for the popleft() method under the deque module in Python.
This entry provides a description of the method, its syntax, an example demonstrating its use, and a runnable Codebyte example.
The goal is to improve Python deque documentation by covering all major methods.

Issue Solved

Closes #7748

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.

[LasVegas98]

Good morning/afternoon/evening, thank you very much for assigning me to this issue and for reviewing. Please let me know if/what changes you need me to make.

[mamtawardhani]

Looks good for a second review 🚀

[dakshdeepHERE]

LGTM 🚀

[github-actions]

👋 @LasVegas98
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