submodules: bump external/sapphire-paratime from 6c67627 to 91341a5

Bumps [external/sapphire-paratime](https://github.com/oasisprotocol/sapphire-paratime) from `6c67627` to `91341a5`.
- [Release notes](https://github.com/oasisprotocol/sapphire-paratime/releases)
- [Commits](oasisprotocol/sapphire-paratime@6c67627...91341a5)

---
updated-dependencies:
- dependency-name: external/sapphire-paratime
  dependency-type: direct:production
...

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