submodules: bump external/cli from aec1603 to c91b7ca

Bumps [external/cli](https://github.com/oasisprotocol/cli) from `aec1603` to `c91b7ca`.
- [Release notes](https://github.com/oasisprotocol/cli/releases)
- [Commits](oasisprotocol/cli@aec1603...c91b7ca)

---
updated-dependencies:
- dependency-name: external/cli
  dependency-version: c91b7ca57954888198d1d2332aa30490eefc7585
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]