Fixed VSA multi-select project dropdown

What does this MR do and why?

Fixes bug where initial project selections are cleared out upon entering a search query and selecting a search result.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After
Screen Recording 2023-09-21 at 6.42.12 PM.mov	Screen Recording 2023-09-21 at 6.43.39 PM.mov

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Please make sure that you're on the GitLab Ultimate plan.
2. Visit VSA for any group with projects and create a value stream if necessary or follow these steps:
   1. run SEED_CYCLE_ANALYTICS=true SEED_VSA=true FILTER=cycle_analytics rake db:seed_fu
   2. Visit the group value stream. The group URL is present in the output of the command above.
   3. Open rails console and run Analytics::CycleAnalytics::ReaggregationWorker.new.perform
   4. Refresh the group value stream and you should see data
3. Verify that the projects dropdown is working correctly:
   1. Use text search to find a project
   2. Select that project
   3. Use text search to find a different project
   4. Select the project
   5. Ensure that the first selection isn't cleared and that there are now two projects selected

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #422206 (closed)