Update associations.md (#771)

Modify a phrase to make the sentence more accurate

pages/docs/associations.md

@@ -147,7 +147,7 @@ db.Select("Account").Delete(&users)
 
 {% note warn %}
 **NOTE:**
-It's important to note that associations will only be deleted if the primary key of the deleting record is not zero. GORM uses these primary keys as conditions to delete the selected associations.
+It's important to note that associations will be deleted only if the primary key of the deleting record is not zero. GORM uses these primary keys as conditions to delete the selected associations.
 
 ```go
 // This will not work as intended