Bump tools/swift-sdk-generator from df46d2f to 685190d

Bumps [tools/swift-sdk-generator](https://github.com/apple/swift-sdk-generator) from `df46d2f` to `685190d`.
- [Commits](swiftlang/swift-sdk-generator@df46d2f...685190d)

---
updated-dependencies:
- dependency-name: tools/swift-sdk-generator
  dependency-type: direct:production
...

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

Author: dependabot[bot]