KT-7918 J2K: don't generate jvmOverloads on private declarations

#KT-7918 Fixed

j2k/testData/fileOrElement/overloads/Private.java

@@ -0,0 +1,10 @@
+class A {
+    private int bar(String s) {
+        System.out.println("s = " + s);
+        return 0;
+    }
+
+    private int bar() {
+        return bar(null);
+    }
+}