add trailing newlines to test files

otherwise I have to rollback dozens of files after using sed that follows conventions

compiler/testData/diagnostics/tests/infos/Autocasts.jet

@@ -250,4 +250,4 @@ fun foo(var a: Any): Int {
         return <!AUTOCAST_IMPOSSIBLE!>a<!>
     }
     return 1
-}
+}

compiler/testData/diagnostics/tests/infos/PropertiesWithBackingFields.jet

@@ -56,4 +56,4 @@ class TestPCParameters(w : Int, x : Int, val y : Int, var z : Int) : Super(w) {
 
   fun foo() = <!UNRESOLVED_REFERENCE!>x<!>
 
-}
+}