Flaky: TestApplicationTest.testStreamingResponse on mingwX64

## Root cause

The test `io.ktor.tests.server.testing.TestApplicationTest.testStreamingResponse` intermittently fails on mingwX64.

**Error:** `Expected , actual <[Client] Test 2>`

The test receives a response line with an unexpected `[Client] ` prefix, suggesting a logging message is being captured in the response stream, or a test isolation issue where log output leaks into the response body on the Windows native platform.

## Reproduction

Fails intermittently on TeamCity mingwX64 builds. Example builds:
- https://ktor.teamcity.com/buildConfiguration/Ktor_KtorMatrixNativeWindowsX64/412039 (PR branch)
- https://ktor.teamcity.com/buildConfiguration/Ktor_KtorCore_All/412003 (release/3.x base branch)

## Impact

This failure is present on the `release/3.x` base branch and affects PRs targeting it intermittently.

Start with io.ktor.tests.server.testing.TestApplicationTest.testStreamingResponse and reproduce it on TeamCity mingwX64 using the linked builds as context. Trace the response stream and logging output around the intermittent failure, then verify that the test consistently receives Test 2 without the [Client] prefix on the Windows native platform.

Written by the indexing model from the issue text.