[BUG]: tests.gateware.core.test_flash.SPIFlashTests is non-deterministic

[lethalbit]

The tests.gateware.core.test_flash.SPIFlashTests test is non-deterministic and randomly fails/passes.

The gateware itself works enough for DFU and applet updates, but the tests being unstable is non-ideal.

This is likely due to how the Torii pysim engine works. So there is no real fix right away, ideally I'd like to be able to formally verify it, but that is much later on the docket.

This issue will likely be around until the new sim engine is in Torii, so just skipping that test might be the best for now