style: fix gofmt formatting in schema_stub.go

Add missing newline at end of file to satisfy gofmt requirements.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: pdfinn

validator/schema_stub.go

@@ -25,4 +25,4 @@ func (s *Schema) Validate(xml []byte) error {
 // Free is a stub method when CGO is disabled
 func (s *Schema) Free() {
 	// No-op when CGO is disabled
-}
+}