Flash: fix flash_suspend example to include worst case

flash_suspend example will now test the worst case in order to be able
to detect real regression:
- shorter response time is acceptable, as the tested function may be in the cache already
- response time longer than 120us will be considered a potential regression

examples/system/flash_suspend/pytest_flash_suspend.py

@@ -14,7 +14,7 @@ def test_flash_suspend_example(dut: Dut) -> None:
     dut.expect_exact('found partition')
     res = dut.expect(r'During Erase, ISR callback function\(in flash\) response time:\s+(\d+(\.\d{1,2})) us')
     response_time = res.group(1).decode('utf8')
-    assert 0 <= float(response_time) < 40
+    assert 0 <= float(response_time) < 120
 
     res = dut.expect(r'During Erase, ISR callback function\(in iram\) response time:\s+(\d+(\.\d{1,2})) us')
     response_time = res.group(1).decode('utf8')