Bump panphon from 0.20.0 to 0.21.2

Bumps [panphon](https://github.com/dmort27/panphon) from 0.20.0 to 0.21.2.
- [Release notes](https://github.com/dmort27/panphon/releases)
- [Commits](https://github.com/dmort27/panphon/commits)

---
updated-dependencies:
- dependency-name: panphon
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

docker_requirements.txt

@@ -16,7 +16,7 @@ nltk==3.6.6
 numpy==1.26.*
 OSKut==1.3
 pandas==1.4.*
-panphon==0.20.0
+panphon==0.21.2
 phunspell==0.1.6
 protobuf==3.20.3
 pyicu==2.8