Add nullability annotations to tests in module/spring-boot-restdocs

See gh-47263

Author: mhalbritter

module/spring-boot-restdocs/build.gradle

@@ -42,3 +42,7 @@ dependencies {
 
 	testRuntimeOnly(project(":module:spring-boot-tomcat"))
 }
+
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}