WEB: Update sponsors and fix logos style
Updating the list of sponsors, @jreback @jorisvandenbossche @jbrockmendel please let me know if I'm mistaken.

Also, fixing the style of the logos, which had the centering wrong, and a border was introduced by mistake:

![Screenshot at 2025-03-14 23-15-34](https://github.com/user-attachments/assets/fe67b218-b68d-4def-ae85-038dddc70a1e)

/preview Website preview of this PR available at: https://pandas.pydata.org/preview/pandas-dev/pandas/61121/