test(root): fix flaky RootProcessRunner inherited-stdout test (#6282)

The test gave RootProcessRunner.run a 250 ms deadline. When sh takes
longer than that to start and finish, the runner hits the deadline,
destroys it and returns -1, and the test fails with
"expected: <0> but was: <-1>". With the sh from Git for Windows this
happened in 6 of 30 runs.

The test's real guard is the 1500 ms elapsed bound against the
background "sleep 5". A 3000 ms deadline leaves that bound alone to
decide the result, so a runner that keeps a finished command open until
its deadline now fails the test as well; with 250 ms it passed.

V2rayNG/app/src/test/java/com/v2ray/ang/root/RootProcessRunnerTest.kt

@@ -13,7 +13,7 @@ class RootProcessRunnerTest {
     }
     @Test fun `inherited stdout cannot hold a completed command open`() {
         val start = System.nanoTime()
-        val result = RootProcessRunner.run(listOf("sh", "-c", "sleep 5 & echo complete"), 250)
+        val result = RootProcessRunner.run(listOf("sh", "-c", "sleep 5 & echo complete"), 3000)
         assertEquals(0, result.code)
         assertTrue(result.output.contains("complete"))
         assertTrue(TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start) < 1500)