message: test(errors): update "immutable" test to have proper types
diff: @@ -19,7 +19,6 @@ import {
  import { DecoratorKeys, WhatIsIt } from '../../src/internal/constants';
  import { _buildSchema } from '../../src/internal/schema';
  import { assertion, assignMetadata, createArrayFromDimensions, mapOptions, mergeSchemaOptions } from '../../src/internal/utils';
  -import { logger } from '../../src/logSettings';
  it('should error if an non-existing(runtime) type is given [InvalidTypeError]', () => {
  try {
  @@ -105,20 +104,17 @@ it('should error if no valid model is supplied to "addModelToTypegoose" [TypeErr
  });
  it('should not modify an immutable', async () => {
  - logger.warn = jest.fn();
  -
  class TestImmutable {
  - @prop({ required: true, immutable: true })
  + @prop({ type: String, required: true, immutable: true })
  public someprop: Readonly<string>;
  }
  const TIModel = getModelForClass(TestImmutable);
  - const doc = await TIModel.create({ someprop: 'Hello' } as TestImmutable);
  + const doc = await TIModel.create({ someprop: 'Hello' });
  expect(doc).not.toBeUndefined();
  doc.someprop = 'Hello2';
  await doc.save();
  expect(doc.someprop).toEqual('Hello');
  - expect((logger.warn as any).mock.calls.length).toEqual(1);
  });
  describe('tests for "NoValidClass"', () => {
  