[gardening]: remove doc comment for nonextant parameter (#363)

Author: jamieQ

Workflow/Sources/WorkflowNode.swift

@@ -121,8 +121,6 @@ final class WorkflowNode<WorkflowType: Workflow> {
 
     /// Internal method that forwards the render call through the underlying `subtreeManager`,
     /// and eventually to the client-specified `Workflow` instance.
-    /// - Parameter isRootNode: whether or not this is the root node of the tree. Note, this
-    /// is currently only used as a hint for the logging infrastructure, and is up to callers to correctly specify.
     /// - Returns: A `Rendering` of appropriate type
     func render() -> WorkflowType.Rendering {
         WorkflowLogger.logWorkflowStartedRendering(ref: self)