remove opt_rel_def in flat_to_closProofTheory

[ordinarymath]

cakeml/compiler/backend/proofs/flat_to_closProofScript.sml

Lines 72 to 76 in 6ddaf6f

	Definition opt_rel_def[simp]:
	opt_rel f NONE NONE = T /\
	opt_rel f (SOME x) (SOME y) = f x y /\
	opt_rel f _ _ = F
	End

OPTREL should be used instead.