multi: replace FundingLocked and funding_locked strings

This commit is created by running the following commands,
```shell
find . -name "*.go" -exec sed -i '' 's/\"FundingLocked/\"ChannelReady/g' {} \;
find . -name "*.go" -exec sed -i '' 's/FundingLocked\"/ChannelReady\"/g' {} \;
find . -name "*.go" -exec sed -i '' 's/\ funding_locked/\ channel_ready/g' {} \;
```

lnwire/message.go

@@ -89,7 +89,7 @@ func (t MessageType) String() string {
 	case MsgFundingSigned:
 		return "MsgFundingSigned"
 	case MsgChannelReady:
-		return "FundingLocked"
+		return "ChannelReady"
 	case MsgShutdown:
 		return "Shutdown"
 	case MsgClosingSigned: