Add nullability annotations to tests in system-test/spring-boot-deployment-system-test

See gh-47263

system-test/spring-boot-deployment-system-tests/build.gradle

@@ -57,4 +57,12 @@ systemTest {
 
 war {
 	archiveVersion = ''
-}
+}
+
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}
+
+tasks.named("compileSystemTestJava") {
+	options.nullability.checking = "tests"
+}