SerializationTest fails with Vaadin 25.1 due to missing jakarta.servlet-api

[javier-godoy]

`SerializationTest` fails when building against Vaadin 25.1.0-rc2 with the v25 profile.

Error:

java.lang.NoClassDefFoundError: jakarta/servlet/http/HttpSessionBindingListener
    at com.flowingcode.vaadin.addons.imagecrop.test.SerializationTest.testSerializationOf(SerializationTest.java:38)
    at com.flowingcode.vaadin.addons.imagecrop.test.SerializationTest.testSerialization(SerializationTest.java:49)
Caused by: java.lang.ClassNotFoundException: jakarta.servlet.http.HttpSessionBindingListener

Root cause: Starting from vaadin-testbench-core:10.1.0-rc1 (Vaadin 25.1.x), the vaadin-testbench-unit dependency was dropped, which previously provided jakarta.servlet:jakarta.servlet-api transitively. This causes SerializationTest to fail at runtime.

Fix: Add an explicit jakarta.servlet:jakarta.servlet-api:6.1.0:test dependency to the v25 profile in pom.xml:

<dependency>
    <groupId>jakarta.servlet</groupId>
    <artifactId>jakarta.servlet-api</artifactId>
    <version>6.1.0</version>
    <scope>test</scope>
</dependency>

Reported via mstahv/vaadin-ecosystem-build#106.