Upgrade to Checkstyle 10.26.1

Closes gh-1640

Author: snicoll

gradle/plugins/conventions-plugin/src/main/java/org/springframework/ws/gradle/conventions/CheckstyleConventions.java

@@ -45,7 +45,7 @@ public void apply(Project project) {
 				.forEach((checkstyle) -> checkstyle.getMaxHeapSize().set("1g"));
 			project.getTasks().named("checkstyleTest").configure((task) -> task.setEnabled(false));
 			CheckstyleExtension checkstyle = project.getExtensions().getByType(CheckstyleExtension.class);
-			checkstyle.setToolVersion("10.24.0");
+			checkstyle.setToolVersion("10.26.1");
 			checkstyle.getConfigDirectory().set(project.getRootProject().file("src/checkstyle"));
 			String version = SpringJavaFormatPlugin.class.getPackage().getImplementationVersion();
 			DependencySet checkstyleDependencies = project.getConfigurations()