fix(initial-value-templates): comment out check for _type

This check currently fails a valid case where you set an initial value for an "anonymous" object field and omit the `_type` in the initial value. E.g. the following valid example will fail unless this line is commented out:

```js
export const initialValuesTest = {
  name: 'initialValuesTest',
  type: 'document',
  fields: [
    {
      name: 'simpleObject',
      title: 'Simple object',
      type: 'object',
      fields: [{name: 'field1', type: 'string'}],
    },
  ],
initialValue: {
    title: 'foo',
    simpleObject: {
      field1: 'hello',
    },
  },
}
```

packages/@sanity/initial-value-templates/src/validate.ts

@@ -114,7 +114,8 @@ function validateValue(value: any, path: (string | number)[] = [], parentIsArray
       // In the case of references, we know what the type should be, so apply it
       initial._type = 'reference'
     } else {
-      throw new Error(`missing "_type" property at path "${pathToString(path)}"`)
+      // todo: consider if we need to re-instantiate this. It currently makes the valid case of having an initial object value for a field fail
+      // throw new Error(`missing "_type" property at path "${pathToString(path)}"`)
     }
   }
 

packages/@sanity/initial-value-templates/test/resolve.test.ts

@@ -70,11 +70,15 @@ describe('resolveInitialValue', () => {
 
   test('throws on wrong value type resolved', () => {
     expect(resolveInitialValue(schema, {...example, value: () => null})).rejects.toMatchObject({
-      message: 'Template "author" initial value: resolved to a non-object',
+      message:
+        'Template "author" has invalid "value" property - must be a plain object or a resolver function returning a plain object',
     })
   })
 
-  test('throws on values with sub-objects missing `_type`', () => {
+  // todo: we should validate based on schema type here and reenable this test
+  //  Currently the initial value validator is not schema aware and fails if resolved initial value is missing _type
+  //  but this doesn't account for fields of type object, which is a valid case for omitting _type.
+  xtest('throws on values with sub-objects missing `_type`', () => {
     expect(
       resolveInitialValue(schema, {
         ...example,