docs: Fix Markdown Lint Errors in Communication Best Practices Guide

[cubxxw]

This PR addresses the Markdown linting errors reported by the CI/CD pipeline for the 11-communication_best_practices.md document within the GSoC Guides repository. The reported issues were primarily related to trailing spaces and the formatting of lists, which could potentially hinder proper rendering on the website. Here are the specific changes made:

• Removed trailing spaces that violated MD009/no-trailing-spaces rule.
• Ensured that lists are surrounded by blank lines, correcting the MD032/blanks-around-lists errors.

By resolving these linting issues, this PR aims to improve the readability and maintainability of the Communication Best Practices guide, ensuring that it adheres to the Markdown standards expected by our documentation pipeline.

Link to the CI/CD error report: CI Error Report

These changes were made in response to the CI/CD process identifying formatting inconsistencies that could affect the presentation of the document. Ensuring that our documentation meets these standards is crucial for maintaining a high-quality guide for GSoC participants.