Migrate `page_bundles/productivity_analytics.scss` page specific styling to CSS utilities

Background

Following on from the work in Convert ee/app/assets/stylesheets/pages/product... (#268016 - closed), we should look at the custom CSS applied to the productivity analytics page from the page_bundles/productivity_analytics.scss file and determine what is still required.

Relevant file

• https://gitlab.com/gitlab-org/gitlab/-/blob/a82a2bf2fc3de50b366d8ffeff31f9a1ff089fe3/ee/app/assets/stylesheets/page_bundles/productivity_analytics.scss

Implementation guide

• https://gitlab-org.gitlab.io/gitlab-ui/tailwind-config-viewer/ contains a list of utility classes that are available
• We should review the CSS styles applied and replace with a relevant CSS utility where possible
• We can use the storybook stories introduced in !166252 (merged) to verify changes