Add clarification for lecture quiz grading rules

[CostinCarabas]

• Add clarification in misc/rules-and-grading.md

Prerequisite Checklist

• Read the contribution guidelines regarding submitting new changes to the project;
• Tested your changes against relevant architectures and platforms;
• Updated relevant documentation (if needed).

Description of changes

Add clarification about how points are granted in quiz lecture in misc/rules-and-grading.md

[razvand]

All good.