chore(types): remove redundant 'undefined' type (#3484)

packages/compiler-core/src/ast.ts

@@ -108,7 +108,7 @@ export interface RootNode extends Node {
   cached: number
   temps: number
   ssrHelpers?: symbol[]
-  codegenNode?: TemplateChildNode | JSChildNode | BlockStatement | undefined
+  codegenNode?: TemplateChildNode | JSChildNode | BlockStatement
 }
 
 export type ElementNode =