zig fmt: fix rendering of struct with no trailing comma on last field

std/zig/parser_test.zig

@@ -1,3 +1,18 @@
+test "zig fmt: no trailing comma on struct decl" {
+    try testTransform(
+        \\const RoundParam = struct {
+        \\    k: usize, s: u32, t: u32
+        \\};
+    ,
+        \\const RoundParam = struct {
+        \\    k: usize,
+        \\    s: u32,
+        \\    t: u32,
+        \\};
+        \\
+    );
+}
+
 test "zig fmt: simple asm" {
     try testTransform(
         \\comptime {

std/zig/render.zig

@@ -102,8 +102,7 @@ fn renderTopLevelDecl(allocator: &mem.Allocator, stream: var, tree: &ast.Tree, i
             }
             try renderToken(tree, stream, field.name_token, indent, Space.None); // name
             try renderToken(tree, stream, tree.nextToken(field.name_token), indent, Space.Space); // :
-            try renderExpression(allocator, stream, tree, indent, field.type_expr, Space.None); // type
-            try renderToken(tree, stream, tree.nextToken(field.lastToken()), indent, Space.Newline); // ,
+            try renderTrailingComma(allocator, stream, tree, indent, field.type_expr, Space.Newline); // type,
         },
 
         ast.Node.Id.UnionTag => {