Add missing functions that do not require parens to the formatter list (#367)

Author: leandrocp

.formatter.exs

@@ -1,20 +1,25 @@
 locals_without_parens = [
   add: 2,
   add: 3,
+  add_if_not_exists: 2,
+  add_if_not_exists: 3,
   alter: 2,
   create: 1,
   create: 2,
   create_if_not_exists: 1,
   create_if_not_exists: 2,
   drop: 1,
+  drop: 2,
   drop_if_exists: 1,
+  drop_if_exists: 2,
   execute: 1,
   execute: 2,
   modify: 2,
   modify: 3,
   remove: 1,
   remove: 2,
   remove: 3,
+  remove_if_exists: 2,
   rename: 2,
   rename: 3,
   timestamps: 1