go/vt/vtgate/schema: bump TestTrackerNoLock channel-send timeout

TestTrackerNoLock pushes 500,000 messages onto a channel and asserts
each send completes within 10ms. Under CI load that's tight enough to
flake regularly, surfacing as:

  tracker_test.go:199: failed to send health check to tracker

Match the fix from PR #18317: bump the per-send timeout to 50ms.

Backport of the go/vt/vtgate/schema/tracker_test.go slice of #18317
(the materializer_test.go slice is for an unrelated test).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Arthur Schreiber <arthur@planetscale.com>

Author: arthurschreiber

go/vt/vtgate/schema/tracker_test.go

@@ -195,7 +195,7 @@ func TestTrackerNoLock(t *testing.T) {
 	for i := 0; i < 500000; i++ {
 		select {
 		case ch <- th:
-		case <-time.After(10 * time.Millisecond):
+		case <-time.After(50 * time.Millisecond):
 			t.Fatalf("failed to send health check to tracker")
 		}
 	}