Don't validate HelpMojo formatting

The `HelpMojo` class is always generated and it should not be checked
for formatting.

See gh-13255

spring-boot-parent/pom.xml

@@ -506,6 +506,11 @@
 				<groupId>io.spring.javaformat</groupId>
 				<artifactId>spring-javaformat-maven-plugin</artifactId>
 				<version>${spring-javaformat.version}</version>
+				<configuration>
+					<excludes>
+						<exclude>**/HelpMojo.java</exclude>
+					</excludes>
+				</configuration>
 				<executions>
 					<execution>
 						<phase>validate</phase>