fix(runtime-dom): ensure readonly type prop on textarea is handled patched as attribute (#2888)

close #2766

Co-authored-by: Thorsten Luenborg <t.luneborg@googlemail.com>

packages/runtime-dom/__tests__/patchProps.spec.ts

@@ -149,4 +149,11 @@ describe('runtime-dom: props patching', () => {
     patchProp(el, 'form', 'foo', null)
     expect(el.getAttribute('form')).toBe(null)
   })
+
+  test('readonly type prop on textarea', () => {
+    const el = document.createElement('textarea')
+    // just to verify that it doesn't throw when i.e. switching a dynamic :is from an 'input' to a 'textarea'
+    // see https://github.com/vuejs/vue-next/issues/2766
+    patchProp(el, 'type', 'text', null)
+  })
 })