Always split collections and argument lists with trailing commas.

test/splitting/arguments.stmt

Index: test/splitting/arguments.stmt
diff --git a/test/splitting/arguments.stmt b/test/splitting/arguments.stmt
index 9ca049da8bf7528499432dfe9bea77a6e2584f84..398b97479e6d9525b706add31ebf22fea2b1e21e 100644
--- a/test/splitting/arguments.stmt
+++ b/test/splitting/arguments.stmt
@@ -201,13 +201,17 @@ function(
   ;
 });
 >>> trailing comma
-functionn(argument,argument  ,argument  ,  );
+fn(argument,argument  ,argument  ,  );
 <<<
-functionn(
-    argument, argument, argument,);
+fn(
+  argument,
+  argument,
+  argument,
+);
 >>> trailing comma in named argument list
-function(named: argument,another:argument,  );
+fn(named: argument,another:argument,  );
 <<<
-function(
-    named: argument,
-    another: argument,);
+fn(
+  named: argument,
+  another: argument,
+);