Remove unused FileNotFoundException import from AttachmentTests

Co-authored-by: thomasturrell <1552612+thomasturrell@users.noreply.github.com>

Author: Copilot

xapi-model/src/test/java/dev/learning/xapi/model/AttachmentTests.java

@@ -15,7 +15,6 @@
 import jakarta.validation.ConstraintViolation;
 import jakarta.validation.Validation;
 import jakarta.validation.Validator;
-import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.net.URI;
 import java.nio.charset.StandardCharsets;