test: vlog: remove floating ASSOC_CLOCK

Signed-off-by: Karol Gugala <kgugala@antmicro.com>

tests/fig42-dff/dff.sim.v

diff --git a/tests/fig42-dff/dff.sim.v b/tests/fig42-dff/dff.sim.v
index 6b7128a..3927929 100644
--- a/tests/fig42-dff/dff.sim.v
+++ b/tests/fig42-dff/dff.sim.v
@@ -9,7 +9,6 @@
 
 	(* CLK_TO_Q="CLK 10e-12" *)
 	output reg Q;
-	(* ASSOC_CLOCK="CLK" *)
 
 	always @ ( posedge CLK ) begin
 		Q <= D;