Update prompts/if/synthesize_solution.txt

prompts/if/synthesize_solution.txt

@@ -10,6 +10,7 @@ You must aim for the following goals:
 - Provide a list of requirements addressed by the solution (provide the requirement IDs in the requirements_ids field only)
 - Please also detail each mechanism and how they work in the final solution description.
 - Please describe the solution in the solution description field.
+- Do not forget to add lineskips between titles when describing the solution in markdown
 </task>
 
 <requirements>