The `must check input for US zip format` integration test fails pretty
consistently in Puppeteer 23.4.0+ with `Expected '12341' to equal
'12345'`. This is reproducible with the `pdf.sandbox.external.js` hack
from https://github.com/mozilla/pdf.js/issues/18396#issuecomment-2211273743.
Investigation uncovered two issues at play here:
1. We do two `clearInput` calls, but don't await processing of the two
sandbox events that are triggered by that action. The three tests that
use `issue14307.pdf` are in different `describe` blocks and therefore
reload the PDF file, so we can simply remove those calls because the
inputs are already empty by default.
2. We don't await processing of the sandbox events that occur after
switching to another text field. This causes the expectation failure
because the typing actions will happen too soon and interfere with
the sandbox event processing. We solve the issue by explicitly
awaiting the sandbox roundtrip.
Moreover, similar to PR #19001 and #18399 we remove any remaining room
for intermittent issues by directly checking for the expected value,
which also results in shorter code.
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