Error when running against LSP v3.16 version of server #3001

When running against the Dart server updated to v3.16 of the spec, it fails to initialise with this error:

Invalid params for initialize: params.capabilities.textDocument.rename.prepareSupportDefaultBehavior must be of type PrepareSupportDefaultBehavior

This is because the version of the vscode-language client that was shipped had prepareSupportDefaultBehavior as a boolean, but it was later changed.