Merge pull request #9204 from ethereum/api-fix

add note to eth_protocolVersion in RPC-API

Author: corwintines

src/content/developers/docs/apis/json-rpc/index.md

@@ -271,7 +271,7 @@ curl -X POST --data '{"jsonrpc":"2.0","method":"net_peerCount","params":[],"id":
 
 ### eth_protocolVersion {#eth_protocolversion}
 
-Returns the current Ethereum protocol version.
+Returns the current Ethereum protocol version. Note that this method is [not available in Geth](https://github.com/ethereum/go-ethereum/pull/22064#issuecomment-788682924).
 
 **Parameters**