flake: TestWorkspaceAgentListeningPorts/LinuxAndWindows/OK_Mainline

[spikecurtis]

Seen while testing locally.

Repeatedly see

    workspaceagents_test.go:1108: expected to not find TCP port 33133 in response

until the test context expires.

The test itself is funadmentally flaky: it creates a listener on the real OS networking stack, verifies it shows up in the list of listening ports, then closes the listener and verfies the port doesn't show up. However, the OS can immediately reuse the port for something else, so there is no guarantee the agent won't see the port still in use, especially on a busy system that runs multiple tests in parallel.