Fixes https://github.com/vector-im/riot-web/issues/13226
This isn't the fastest route, but it is a predictable route for the happy path we probably want to test. For example, Alice will already be staring at the DM and could easily accept the verification there, but we probably want to make sure that the toast is present and does the right thing. Similarly, neither of them need to verify that there's green shields everywhere, they should be implied, however an explicit check follows a real user's gaze.
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