Update links on QA Use Case docs (#8784)

- Description: 2 links were not working on Question Answering Use Cases
documentation page. Hence, changed them to nearest useful links,
  - Issue: NA,
  - Dependencies: NA,
  - Tag maintainer: @baskaryan,
  - Twitter handle: NA

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docs/extras/use_cases/question_answering/index.mdx

@@ -138,9 +138,9 @@ len(docs_svm)
     4
 
 Some common ways to improve on vector similarity search include:
-- `MultiQueryRetriever` [generates variants of the input question](/docs/modules/data_connection/retrievers/how_to/MultiQueryRetriever) to improve retrieval.
+- `MultiQueryRetriever` [generates variants of the input question](/docs/modules/data_connection/retrievers/MultiQueryRetriever) to improve retrieval.
 - `Max marginal relevance` selects for [relevance and diversity](https://www.cs.cmu.edu/~jgc/publication/The_Use_MMR_Diversity_Based_LTMIR_1998.pdf) among the retrieved documents.
-- Documents can be filtered during retrieval using [`metadata` filters](/docs/use_cases/question_answering/document-context-aware-QA).
+- Documents can be filtered during retrieval using [`metadata` filters](/docs/use_cases/question_answering/how_to/document-context-aware-QA).
 
 
 ```python