Opensearch retrievers docstrings show the old filters syntax

[anakin87]

haystack-core-integrations/integrations/opensearch/src/haystack_integrations/components/retrievers/opensearch/bm25_retriever.py

Lines 187 to 188 in 6b07663

	retriever.run(query="Why did the revenue increase?",
	filters={"years": ["2019"], "quarters": ["Q1", "Q2"]})

This is just an example, but we should also check the Embedding Retriever and replace the examples with others showing the new filters syntax.