Community Partners: formatting

[reshamas]

@OriolAbril
Should we try having 3 community partner logos in a row, instead of the current 2?

[OriolAbril]

This is defined in the grid directive (:::{grid} ) the numbers that come right after (the main argument in the sphinx primer reference) are the number of columns in different screen sizes.

Docs on grid directive: https://sphinx-design.readthedocs.io/en/sbt-theme/grids.html

Sphinx-primer reference: https://sphinx-primer.readthedocs.io/en/latest/core/directives.html