Improve pinecone hybrid search retriever adding metadata support (#5098)

# Improve pinecone hybrid search retriever adding metadata support

I simply remove the hardwiring of metadata to the existing
implementation allowing one to pass `metadatas` attribute to the
constructors and in `get_relevant_documents`. I also add one missing pip
install to the accompanying notebook (I am not adding dependencies, they
were pre-existing).

First contribution, just hoping to help, feel free to critique :) 
my twitter username is `@andreliebschner`

While looking at hybrid search I noticed #3043 and #1743. I think the
former can be closed as following the example right now (even prior to
my improvements) works just fine, the latter I think can be also closed
safely, maybe pointing out the relevant classes and example. Should I
reply those issues mentioning someone?

@dev2049, @hwchase17

---------

Co-authored-by: Andreas Liebschner <a.liebschner@shopfully.com>

docs/modules/indexes/retrievers/examples/pinecone_hybrid_search.ipynb

@@ -24,7 +24,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "#!pip install pinecone-client"
+    "#!pip install pinecone-client pinecone-text"
    ]
   },
   {