Bump lodash in /src/wp-content/themes/twentynineteen

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

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

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

Author: dependabot[bot]