Reduce number of documents to return for Pinecone (langchain-ai#2299)

Minor change: Currently, Pinecone is returning 5 documents instead of
the 4 seen in other vectorstores, and the comments this Pinecone script
itself. Adjusted it from 5 to 4.

langchain/vectorstores/pinecone.py

@@ -90,7 +90,7 @@ def add_texts(
     def similarity_search_with_score(
         self,
         query: str,
-        k: int = 5,
+        k: int = 4,
         filter: Optional[dict] = None,
         namespace: Optional[str] = None,
     ) -> List[Tuple[Document, float]]:
@@ -125,7 +125,7 @@ def similarity_search_with_score(
     def similarity_search(
         self,
         query: str,
-        k: int = 5,
+        k: int = 4,
         filter: Optional[dict] = None,
         namespace: Optional[str] = None,
         **kwargs: Any,