Fix compilation error in tests

src/stack.zig

@@ -26,7 +26,7 @@ pub fn Fixed(comptime Element: type) type {
             return io.Writer.wrap(Self, self, struct {
                 fn write(stack: *Self, buffer: []const u8) usize {
                     stack.pushAll(buffer) catch |err| switch (err) {
-                        error.Overflow => return 0,
+                        error.OutOfMemory => return 0,
                     };
 
                     return buffer.len;