Bump tools/swift-sdk-generator from 26a65a0 to 13c0c51

Bumps [tools/swift-sdk-generator](https://github.com/apple/swift-sdk-generator) from `26a65a0` to `13c0c51`.
- [Commits](swiftlang/swift-sdk-generator@26a65a0...13c0c51)

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

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

Author: dependabot[bot]