Bump fast-xml-parser in /firestore-activity-feeds/functions

Bumps [fast-xml-parser](https://github.com/NaturalIntelligence/fast-xml-parser) from 5.5.9 to 5.7.2.
- [Release notes](https://github.com/NaturalIntelligence/fast-xml-parser/releases)
- [Changelog](https://github.com/NaturalIntelligence/fast-xml-parser/blob/master/CHANGELOG.md)
- [Commits](NaturalIntelligence/fast-xml-parser@v5.5.9...v5.7.2)

---
updated-dependencies:
- dependency-name: fast-xml-parser
  dependency-version: 5.7.1
  dependency-type: indirect
...

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