e2e: Fix flaky runtime governance test #6483
Description
Fails:
- https://buildkite.com/oasisprotocol/oasis-core-ci/builds/16638#019d2486-4e81-459d-b58d-c91e38a09f4b
- https://buildkite.com/oasisprotocol/oasis-core-ci/builds/16638#019d26f8-ce01-461d-8961-c0dcef294781
Succeeds: https://buildkite.com/oasisprotocol/oasis-core-ci/builds/16638#019d2968-bb6e-4560-85b3-7e4be4ab9d1a