Bump lodash in /fixtures/packaging/systemjs-builder/prod

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.21 to 4.18.1.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](https://github.com/lodash/lodash/compare/4.17.21...4.18.1)

---
updated-dependencies:
- dependency-name: lodash
  dependency-version: 4.18.1
  dependency-type: indirect
...

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