Slight more performant way of updating set (#434)

decompiler/pipeline/commons/expressionpropagationcommons.py

@@ -363,7 +363,7 @@ def _get_dangerous_relations_between_definition_and_target(self, alias_variable:
         for basic_block in self._cfg:
             for instruction in basic_block:
                 if isinstance(instruction, Relation) and instruction.destination.name == alias_variable.name:
-                    relations |= {instruction}
+                    relations.add(instruction)
 
         return relations