I guess if we use both the client and server implementations here we won't notice this as both are using the same wrong names.

However trying to make this interoperate with lsp4j's implementation which actually uses the correct names things break with error like these:

[pool-2-thread-1] ERROR org.springframework.ide.vscode.commons.util.Log - Error
org.eclipse.lsp4j.jsonrpc.ResponseErrorException: Unhandled method client/registerCapability

This seems to be the problem: https://github.com/Microsoft/vscode-languageserver-node/blob/143fb3928737db949bb800ba27d1c6580ad0c024/client/src/protocol.ts#L95

Also the name for unregisterFeature seems to be wrong as well.