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

idea/testData/checker/PrimaryConstructors.kt

@@ -0,0 +1,14 @@
+class X {
+  <error>val x : Int</error>
+}
+
+open class Y() {
+  val x : Int = 2
+}
+
+class Y1 {
+  val x : Int get() = 1
+}
+
+class Z : Y() {
+}