remove double load for zoekt multi-result

What does this MR do and why?

Fix double load of results. On zoekt multi-result page the legacy query needed to be disabled.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

1. Enable the forks filter FF

   echo 'Feature.enable(:zoekt_multimatch_frontend)' | rails c

2. Make sure advanced search is installed and enabled
3. Make sure you enable zoekt.
4. Visit search page http://gdk.test:3000/search?scope=blobs&search=test
5. Search code using namespace where zoekt is enabled (Flightjs)
6. When multi-match results load make sure the ES was called only once
7. When you fill in search term on the multi-match hitting enter won't reload page

Related to #481985 (closed)