Fix ERC721URIStorage description in docs

docs/modules/ROOT/pages/erc721.adoc

@@ -40,7 +40,7 @@ contract GameItem is ERC721URIStorage {
 }
 ----
 
-The xref:api:token/ERC721.adoc#ERC721URIStorage[`ERC721URIStorage`] contract is an implementation of ERC721 that includes all standard extensions (xref:api:token/ERC721.adoc#IERC721Metadata[`IERC721Metadata`] and xref:api:token/ERC721.adoc#IERC721Enumerable[`IERC721Enumerable`]). That's where the xref:api:token/ERC721.adoc#ERC721-_setTokenURI-uint256-string-[`_setTokenURI`] method comes from: we use it to store an item's metadata.
+The xref:api:token/ERC721.adoc#ERC721URIStorage[`ERC721URIStorage`] contract is an implementation of ERC721 that includes the metadata standard extensions (xref:api:token/ERC721.adoc#IERC721Metadata[`IERC721Metadata`]) as well as a mechanism for per-token metadata. That's where the xref:api:token/ERC721.adoc#ERC721-_setTokenURI-uint256-string-[`_setTokenURI`] method comes from: we use it to store an item's metadata.
 
 Also note that, unlike ERC20, ERC721 lacks a `decimals` field, since each token is distinct and cannot be partitioned.