Bump tools/swift-sdk-generator from a0ff972 to df46d2f

Bumps [tools/swift-sdk-generator](https://github.com/apple/swift-sdk-generator) from `a0ff972` to `df46d2f`.
- [Commits](swiftlang/swift-sdk-generator@a0ff972...df46d2f)

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

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

Author: dependabot[bot]