submodules: bump external/cli from 1b97709 to 50f6c7c

Bumps [external/cli](https://github.com/oasisprotocol/cli) from `1b97709` to `50f6c7c`.
- [Release notes](https://github.com/oasisprotocol/cli/releases)
- [Commits](oasisprotocol/cli@1b97709...50f6c7c)

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

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