Fix typo

See gh-17132

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/junit/GradleCompatibilityExtension.java

@@ -30,7 +30,7 @@ import org.springframework.boot.gradle.testkit.GradleBuildExtension;
 
 /**
  * {@link Extension} that runs {@link TestTemplate templated tests} against multiple
- * versions of Gradle. Test classes using the extension must have non-privaten and
+ * versions of Gradle. Test classes using the extension must have non-private and
  * non-final {@link GradleBuild} field named {@code gradleBuild}.
  *
  * @author Andy Wilkinson