cpu.8080: fix stack effects.

extra/cpu/8080/emulator/emulator.factor

@@ -1399,7 +1399,7 @@ SYNTAX: cycles
   #! Set the number of cycles for the last instruction that was defined.
   scan-token string>number last-opcode get-global instruction-cycles set-nth ;
 
-SYNTAX: opcode ( -- )
+SYNTAX: opcode
   #! Set the opcode number for the last instruction that was defined.
   last-instruction get-global 1quotation scan-token hex>
   dup last-opcode set-global set-instruction ;