fix(davinci-client): remove try/catch from update dispatch — errors are now state

We identified two root causes: the PR inadvertently blocked PollingCollector string value updates in the reducer, breaking the e2e polling flow that relies on updater(status) to write terminal statuses before form submission, and two unit tests were left using toThrowError assertions despite the reducer no longer throwing. These changes restore PollingCollector update behaviour via the existing SingleValueAutoCollector path and update the stale tests to assert on collector.error state instead.