Bump brace-expansion from 1.1.15 to 1.1.21 in /source_code

Bumps [brace-expansion](https://github.com/juliangruber/brace-expansion) from 1.1.15 to 1.1.21.
- [Release notes](https://github.com/juliangruber/brace-expansion/releases)
- [Commits](juliangruber/brace-expansion@v1.1.15...v1.1.21)

---
updated-dependencies:
- dependency-name: brace-expansion
  dependency-version: 1.1.21
  dependency-type: indirect
...

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Author: dependabot[bot]