Remove usages of array_list.Managed in docs/wasm/markdown

lib/docs/wasm/markdown.zig

@@ -1119,9 +1119,9 @@ fn testRender(input: []const u8, expected: []const u8) !void {
     var doc = try parser.endInput();
     defer doc.deinit(testing.allocator);
 
-    var actual = std.array_list.Managed(u8).init(testing.allocator);
+    var actual: std.Io.Writer.Allocating = .init(testing.allocator);
     defer actual.deinit();
-    try doc.render(actual.writer());
+    try doc.render(&actual.writer);
 
-    try testing.expectEqualStrings(expected, actual.items);
+    try testing.expectEqualStrings(expected, actual.written());
 }

lib/docs/wasm/markdown/Document.zig

@@ -160,8 +160,8 @@ pub fn deinit(doc: *Document, allocator: Allocator) void {
 }
 
 /// Renders a document directly to a writer using the default renderer.
-pub fn render(doc: Document, writer: anytype) @TypeOf(writer).Error!void {
-    const renderer: Renderer(@TypeOf(writer), void) = .{ .context = {} };
+pub fn render(doc: Document, writer: *std.Io.Writer) std.Io.Writer.Error!void {
+    const renderer: Renderer(void) = .{ .context = {} };
     try renderer.render(doc, writer);
 }