build: update load-grunt-tasks requirement to ^4.0.0 in /integrationTest (#739)
build: update load-grunt-tasks requirement to ^4.0.0 in /integrationTest (#739)

Updates the requirements on [load-grunt-tasks](https://github.com/sindresorhus/load-grunt-tasks) to permit the latest version.
- [Release notes](https://github.com/sindresorhus/load-grunt-tasks/releases)
- [Commits](https://github.com/sindresorhus/load-grunt-tasks/commits/v4.0.0)

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