[testing] marking down all jackson related tests as j8+ only

The jackson dep we need for testing is too new a class file to run on j6, stubbing it out too much effort.
Odds we find a bug specifically because this stuff fails on java6/7 are low, and I'm okay with supporting
6/7 a little less well.

test/transform/resource/before/JacksonJsonProperty.java

@@ -1,4 +1,4 @@
-//version 8:
+//version 8: Jackson deps are at least Java7+.
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonSetter;
 import com.fasterxml.jackson.annotation.Nulls;