Bump semver and mongodb in /examples/AWS/AWS-ECS/app

Removes [semver](https://github.com/npm/node-semver). It's no longer used after updating ancestor dependency [mongodb](https://github.com/mongodb/node-mongodb-native). These dependencies need to be updated together.


Removes `semver`

Updates `mongodb` from 3.3.3 to 3.7.4
- [Release notes](https://github.com/mongodb/node-mongodb-native/releases)
- [Changelog](https://github.com/mongodb/node-mongodb-native/blob/main/HISTORY.md)
- [Commits](mongodb/node-mongodb-native@v3.3.3...v3.7.4)

---
updated-dependencies:
- dependency-name: semver
  dependency-type: indirect
- dependency-name: mongodb
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]