Fix flaky test_command_output_continuation test in BashSession

[rbren]

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• Include this change in the Release Notes. If checked, you must provide an end-user friendly description for your change below

End-user friendly description of the problem this fixes or functionality this introduces.
Fixes a flaky test in the BashSession class that was intermittently failing due to timing issues.

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Summarize what the PR does, explaining any non-trivial design decisions.
This PR modifies the test_command_output_continuation test to be more robust against timing issues. The test was failing because it expected specific output patterns that could vary depending on execution timing.

The updated test now:

1. Uses a more robust approach that handles both cases where the command completes immediately or times out
2. Verifies all expected numbers (1-5) appear in the output without requiring them to appear in separate observations
3. Removes assertions that were sensitive to timing and implementation details

This makes the test more reliable while still verifying the core functionality of command output continuation.

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Link of any specific issues this addresses:
No specific issue, but this addresses a flaky test that was recently introduced.

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To run this PR locally, use the following command:

docker run -it --rm   -p 3000:3000   -v /var/run/docker.sock:/var/run/docker.sock   --add-host host.docker.internal:host-gateway   -e SANDBOX_RUNTIME_CONTAINER_IMAGE=docker.all-hands.dev/all-hands-ai/runtime:5e7a547-nikolaik   --name openhands-app-5e7a547   docker.all-hands.dev/all-hands-ai/openhands:5e7a547

[tofarr]

This one has been annoying me!

[ryanhoangt]

LGTM!