Bump sp-transaction-pool from bca8a29 to ff24c60

Bumps [sp-transaction-pool](https://github.com/paritytech/substrate) from `bca8a29` to `ff24c60`.
- [Release notes](https://github.com/paritytech/substrate/releases)
- [Commits](paritytech/substrate@bca8a29...ff24c60)

---
updated-dependencies:
- dependency-name: sp-transaction-pool
  dependency-type: direct:production
...

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