Revert "Merge branch '373285-fix-n-1-queries-for-epic-label_links' into 'master'"

What does this MR do and why?

With !97705 (merged) we preloaded label_links association for labels when querying epics. The resulting query can be very slow if there is a large number of labels resulting in degraded performance.

Query plan (internal)

The previous N+1 queries were:

SELECT "labels".* FROM "labels" INNER JOIN "label_ links" ON "labels"."id" = "label links"."label
_id" WHERE "label _links"."target_id" = 374092 AND "label_links"."target _type" = 'Epic' ORDER BY "labels". "title" ASC, "labels"."id" DESC LIMIT 100

MR acceptance checklist

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