Fix from_embeddings method examples (#3174)

Fix examples for `from_embeddings` method for annoy and faiss
vectorstores

langchain/vectorstores/annoy.py

@@ -367,7 +367,9 @@ class Annoy(VectorStore):
                 from langchain import Annoy
                 from langchain.embeddings import OpenAIEmbeddings
                 embeddings = OpenAIEmbeddings()
-                db = Annoy.from_texts(texts, embeddings)
+                text_embeddings = embeddings.embed_documents(texts)
+                text_embedding_pairs = list(zip(texts, text_embeddings))
+                db = Annoy.from_embeddings(text_embedding_pairs, embeddings)
         """
         texts = [t[0] for t in text_embeddings]
         embeddings = [t[1] for t in text_embeddings]

langchain/vectorstores/faiss.py

@@ -396,7 +396,9 @@ class FAISS(VectorStore):
                 from langchain import FAISS
                 from langchain.embeddings import OpenAIEmbeddings
                 embeddings = OpenAIEmbeddings()
-                faiss = FAISS.from_texts(texts, embeddings)
+                text_embeddings = embeddings.embed_documents(texts)
+                text_embedding_pairs = list(zip(texts, text_embeddings))
+                faiss = FAISS.from_embeddings(text_embedding_pairs, embeddings)
         """
         texts = [t[0] for t in text_embeddings]
         embeddings = [t[1] for t in text_embeddings]