Apply suggestion to soitool/database.py

soitool/database.py

@@ -344,7 +344,7 @@ class Database:
     def insert_soi(self, soi):
         """Serialize, compress and insert SOI into database-table SOI.
 
-        If one or more SOI's with the same title exist in db, (1), (2), ...
+        If one or more SOI's with the same title exist in db, '(1)', '(2)', ...
         is added to the Title-column of the SOI to insert.
 
         Parameters