Bump emmet-core from 0.21.19 to 0.21.20 (#540)

Bumps [emmet-core](https://github.com/materialsproject/emmet) from 0.21.19 to 0.21.20.
- [Release notes](https://github.com/materialsproject/emmet/releases)
- [Changelog](https://github.com/materialsproject/emmet/blob/main/docs/CHANGELOG.md)
- [Commits](materialsproject/emmet@v0.21.19...v0.21.20)

---
updated-dependencies:
- dependency-name: emmet-core
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements.txt

@@ -4,6 +4,6 @@ typing-extensions==4.0.1
 maggma==0.40.0
 requests==2.27.1
 monty==2022.1.19
-emmet-core==0.21.19
+emmet-core==0.21.20
 mpcontribs-client>=4.2.9