fix(types): fix types for readonly ref

fix #4180

packages/reactivity/src/ref.ts

@@ -19,11 +19,6 @@ export interface Ref<T = any> {
    * @internal
    */
   _shallow?: boolean
-
-  /**
-   * Deps are maintained locally rather than in depsMap for performance reasons.
-   */
-  dep?: Dep
 }
 
 type RefBase<T> = {

test-dts/reactivity.test-d.ts

@@ -1,4 +1,4 @@
-import { readonly, describe, expectError } from './index'
+import { ref, readonly, describe, expectError, expectType, Ref } from './index'
 
 describe('should support DeepReadonly', () => {
   const r = readonly({ obj: { k: 'v' } })
@@ -7,3 +7,9 @@ describe('should support DeepReadonly', () => {
   // @ts-expect-error
   expectError((r.obj.k = 'x'))
 })
+
+// #4180
+describe('readonly ref', () => {
+  const r = readonly(ref({ count: 1 }))
+  expectType<Ref>(r)
+})