Add more space between the columns in the `sidebar with navigation` pattern

[knice]

From Lisa:

Can we tweak a pattern that is live in WP? It is the page layout pattern with the menu on left and then a paragraph. The 'gutter' space between the two needs to be bigger. This feels right to me: https://socialsciences.wordpress.ucsc.edu/departments-and-programs/lals/about-latin-american-and-latino-studies/. this is the default and it is too close: https://socialsciences.wordpress.ucsc.edu/research-subfields/