Minor change to test for #56: annotations needed due to FasterXML/jackson-databind#5466 (#1066)

Author: cowtowncoder

src/test/kotlin/tools/jackson/module/kotlin/test/github/Github56.kt

@@ -10,7 +10,10 @@ import kotlin.test.assertEquals
 class TestGithub56 {
     data class TestGalleryWidget_BAD(
             val widgetReferenceId: String,
-            @JsonUnwrapped var gallery: TestGallery
+            // IMPORTANT! Need _at least_ @get one (@param optional, not sufficient)
+            // (see https://github.com/FasterXML/jackson-databind/pull/5466 for change
+            // that made this necessary in 3.1 )
+            @get:JsonUnwrapped var gallery: TestGallery
     )
 
     data class TestGalleryWidget_GOOD(val widgetReferenceId: String) {