Update llama_cpp.md (#284)

Fixing import of InMemoryDocumentStore

Author: sepastian

integrations/llama_cpp.md

@@ -191,7 +191,7 @@ from haystack.components.builders.prompt_builder import PromptBuilder
 from haystack.components.embedders import SentenceTransformersDocumentEmbedder, SentenceTransformersTextEmbedder
 from haystack.components.retrievers import InMemoryEmbeddingRetriever
 from haystack.components.writers import DocumentWriter
-from haystack.document_stores import InMemoryDocumentStore
+from haystack.document_stores.in_memory import InMemoryDocumentStore
 
 # Import LlamaCppGenerator
 from haystack_integrations.components.generators.llama_cpp import LlamaCppGenerator