test(proxy): accept a reset as the closed connection after revocation

[radim10]

Summary

• revoked_proxy_rejects_requests_without_closing_the_listener failed on Windows at random (seen on fix(run): say how to build a missing sandbox image when nobody can be asked #65): called Result::unwrap() on an Err value: ConnectionReset (os error 10054). After a session is revoked the proxy drops existing connections, and the test expected a clean EOF. On Windows the same drop sometimes arrives as a reset, depending on timing.
• The test now accepts EOF, ConnectionReset or ConnectionAborted. It still fails if the connection stays open (2 s timeout) or receives data, so it still catches a real regression. No product code changes.
• No other proxy test asserts a clean close, so this was the only one affected.

Test plan

• The test passes locally 5 runs in a row
• cargo fmt --check and full cargo test pass
• Windows CI on this PR (the timing can't be reproduced on macOS; one green run doesn't prove a timing flake is gone, but the error that failed fix(run): say how to build a missing sandbox image when nobody can be asked #65 is now accepted)