Minor. Move tests

compiler/testData/codegen/box/specialBuiltins/throwable.kt

@@ -0,0 +1,10 @@
+fun box(): String {
+    try {
+        throw Throwable("OK", null)
+    } catch (t: Throwable) {
+        if (t.cause != null) return "fail 1"
+        return t.message!!
+    }
+
+    return "fail 2"
+}