Fix typos (#5323)

# Documentation typo fixes

Fixes # (issue)

Simple typos in the blockchain .ipynb documentation

docs/modules/indexes/document_loaders/examples/blockchain.ipynb

@@ -19,6 +19,7 @@
    ]
   },
   {
+   "attachments": {},
    "cell_type": "markdown",
    "metadata": {
     "id": "juAmbgoWD17u"
@@ -29,7 +30,7 @@
     "Initially this Loader supports:\n",
     "\n",
     "*   Loading NFTs as Documents from NFT Smart Contracts (ERC721 and ERC1155)\n",
-    "*   Ethereum Maninnet, Ethereum Testnet, Polgyon Mainnet, Polygon Testnet (default is eth-mainnet)\n",
+    "*   Ethereum Mainnnet, Ethereum Testnet, Polygon Mainnet, Polygon Testnet (default is eth-mainnet)\n",
     "*   Alchemy's getNFTsForCollection API\n",
     "\n",
     "It can be extended if the community finds value in this loader.  Specifically:\n",