[x86] Fixed bug in new TEST optimisation where a FLAGS check always returned "in use"
This merge request fixes the order that some instructions are removed in the TEST optimisations !95 (merged) and !96 (merged) - one of the FLAGS checks would always logically return "in use" because a Jcc instruction was only removed AFTER the check. Now, the conditional branch is removed first and hence RegUsedAfterInstruction can evaluate the use of FLAGS after that jump.