Renamed *.jet to *.kt in test data of JetPsiCheckerTest.

idea/testData/checker/regression/Jet72.kt

@@ -0,0 +1,17 @@
+// JET-72 Type inference doesn't work when iterating over ArrayList
+
+import java.util.ArrayList
+
+abstract class Item(val room: <warning>Object</warning>) {
+   abstract val name : String
+}
+
+val items: ArrayList<Item> = ArrayList<Item>()
+
+fun test(room : <warning>Object</warning>) {
+  for(val item: Item in items) {
+    if (item.room === room) {
+      System.out.println("You see " + item.name)
+    }
+  }
+}