Widen T12545 acceptance window
This test has been the scourge of contributors for a long time.
It has caused many failed CI runs and wasted hours debugging a test which barely does anything. The fact is does nothing is the reason for the flakiness and it's very sensitive to small changes in initialisation costs, in particular adding wired-in things can cause this test to fluctuate quite a bit.
Therefore we admit defeat and just bump the threshold up to 10% to catch very large regressions but otherwise don't care what this test does.