fix: changed a type for AsyncComponentFactory component(fix #10252)

[NataliaTepluhina]

What kind of change does this PR introduce? (check at least one)

• [x] Bugfix
• [ ] Feature
• [ ] Code style update
• [ ] Refactor
• [ ] Build-related changes
• [ ] Other, please describe:

Does this PR introduce a breaking change? (check one)

• [ ] Yes
• [x] No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• [x] It's submitted to the dev branch for v2.x (or to a previous version branch), not the master branch
• [x] When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• [x] All tests are passing: https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md#development-setup
• [x] New/updated tests are included

If adding a new feature, the PR's description includes:

• [ ] A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information: Close #10252

[NataliaTepluhina]

@posva added a test as requested 😅

[leobasilio]

I've just spent a couple of hours trying to figure out what was wrong with my code and it turns out this was the problem... Any special reason this PR has not been merged yet? If by any chance the author isn't available anymore, is there any way I could take over this issue?

[Deweloper94]

000201