Fix FAQ link to point at the relevance tutorial directly

The FAQ linked to /documentation/tutorials-search-engineering/retrieval-quality/,
which only exists as a Hugo alias on the ANN recall tutorial. Aliases emit
HTML redirects but not Markdown ones, so the link checker hits the .md
output and 404s. The surrounding prose (golden query set, NDCG@10) is
relevance-tutorial territory anyway.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

qdrant-landing/content/documentation/faq/qdrant-fundamentals.md

@@ -152,7 +152,7 @@ Both methods combine scores from multiple retrieval legs (for example, dense and
 
 For custom fusion, use the [Formula Query](/documentation/search/search-relevance/#score-boosting). For example, you can use decay functions to normalize both scores to a 0-1 range and then fuse them. This approach requires you to determine the approximate score distribution for each corpus, since you can't set decay function parameters dynamically. The Formula Query doesn't support custom rank-based fusion because it doesn't have access to prefetch ranks; only to the raw scores.
 
-To evaluate which works better for your use case, create a small golden query set and compare [retrieval quality metrics](/documentation/tutorials-search-engineering/retrieval-quality/) (for example, NDCG@10) under each method.
+To evaluate which works better for your use case, create a small golden query set and compare [retrieval quality metrics](/documentation/improve-search/retrieval-relevance/) (for example, NDCG@10) under each method.
 
 See also: [Hybrid Queries](/documentation/search/hybrid-queries/)