build: bump @types/prettier from 1.12.2 to 1.12.3 in /packages/stryker (#792)
build: bump @types/prettier from 1.12.2 to 1.12.3 in /packages/stryker (#792)

Bumps [@types/prettier](https://github.com/DefinitelyTyped/DefinitelyTyped) from 1.12.2 to 1.12.3.
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
stryker-mutator/stryker,stryker-mutator/stryker,stryker-mutator/stryker