Fix inaccurate description of RoPE paper findings

[johnhaofu]

• Corrected the description to clarify that the paper shows removing (not rotating) lowest frequencies improves performance
• The original paper (arXiv:2410.06205) proposes p-RoPE which removes lowest frequencies, not rotates them
• This addresses the misleading summary that suggested rotation of low frequencies was beneficial

[johnhaofu]

Note for Reviewers

This is a correction of factual error, not a new blog post. The checklist items in "Preparing the Article" don't apply here as this PR only fixes an inaccurate description of research findings in an existing article.

What was changed:

• Single line correction in designing-positional-encoding.md
• Changed misleading description about RoPE paper findings
• Clarified that the paper proposes removing (not rotating) lowest frequencies

Why this matters:

The original description could mislead readers about the actual research findings from the DeepMind paper (arXiv:2410.06205).

No new assets, thumbnails, or blog metadata changes are needed for this correction.

[merveenoyan]

@FL33TW00D

[FL33TW00D]

Thanks for the tag @merveenoyan.

Thanks for raising this @johnhaofu, you're correct.