Fix metadata package link (polkadot-js#3458)

README.md

@@ -21,7 +21,7 @@ The API is split up into a number of internal packages -
 
 - [@polkadot/api](packages/api/) The API library, providing both Promise and RxJS Observable-based interfaces. This is the main user-facing entry point.
 - [@polkadot/api-derive](packages/api-derive/) Derived results that are injected into the API, allowing for combinations of various query results (only used internally and exposed on the Api instances via `api.derive.*`)
-- [@polkadot/api-metadata](packages/api-metadata/) Base extrinsic, storage and constant injectors for injection
+- [@polkadot/metadata](packages/metadata/) Base extrinsic, storage and constant injectors for injection
 - [@polkadot/rpc-core](packages/rpc-core/) Wrapper around all [JSON-RPC methods](https://polkadot.js.org/docs/substrate/rpc) exposed by a Polkadot network client
 - [@polkadot/rpc-provider](packages/rpc-provider/) Providers for connecting to nodes, including WebSockets and Http