search facet accessibility fixes

[gumaerc]

What are the relevant tickets?

Closes https://github.com/mitodl/hq/issues/5421
Closes https://github.com/mitodl/hq/issues/5429

Description (What does it do?)

This PR takes advantage of the facet-transitioning class added in mitodl/course-search-utils#146, allowing us to set visibility: hidden on facet-visible items while they are not expanded or transitioning. The default color of the expand / collapse caret on facets was also changed to silverGrayDark in accordance with https://github.com/mitodl/hq/issues/5429.

How can this be tested?

First, we will need to get a new version of course-search-utils

• Clone course-search-utils on the cg/add-facet-transitioning-class branch: https://github.com/mitodl/course-search-utils
• Once you are on the correct branch, run yarn install and then yarn typescript to generate the library
• Back in mit-learn, overwrite the contents of the node_modules/@mitodl/course-search-utils/dist folder with the contents of course-search-utils/dist that we just built
• Spin up mit-learn on the cg/facet-accessibility branch
• Make sure you have some data backpopulated in your database and a search index built
• Browse to the search page at https://localhost:8062/search
• Collapse one of the search facets on the left hand side, then right click on the facet and click Inspect
• Look at the facet-visible items within the collapsed facet and ensure they have the visibility: hidden rule applied to them
• Expand the facet while watching the CSS rules on one of the facet-visible items
• Verify that the visibility: hidden rule is removed

Checklist:

• Merge and release add facet-transitioning class course-search-utils#146
• Update the version of course-search-utils in package.json with the newly released version in this PR before merging it

[shanbady]

When testing this I'm seeing certain facets have the visibility set to hidden but not all of them. For example the topics and department filters still had .facet-visible elements with visibility:visible when hidden.

[gumaerc]

@shanbady Thanks, this should be ready for another look

[shanbady]

👍