Fixing mocked asyncWithLDProvider to return Promise

[SHND]

Requirements

• [x] I have added test coverage for new or changed functionality
• [x] I have followed the repository's pull request submission guidelines
• [ ] I have validated my changes against all supported platform versions

Related issues

https://github.com/launchdarkly/jest-launchdarkly-mock/issues/16

Describe the solution you've provided

This is a fix for mockAsyncWithLDProvider. From the docs asyncWithLDProvider should return a Promise. This promise should resolved to a React component. This resolved React component on the good path, should render the children that are passed to it through its props.

Describe alternatives you've considered

Additional context

[yusinto]

Thank you @SHND I'll make sure this gets included in the next release.