Add nullability annotations to tests in smoke-test/spring-boot-smoke-test-aspectj

See gh-47263

smoke-test/spring-boot-smoke-test-aspectj/build.gradle

@@ -24,4 +24,8 @@ dependencies {
 	implementation(project(":starter:spring-boot-starter-aspectj"))
 
 	testImplementation(project(":starter:spring-boot-starter-test"))
-}
+}
+
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}