empty method: do not warn if sync was added (IDEADEV-40820)

java/java-tests/testData/inspection/emptyMethod/superWithoutSync/expected.xml

@@ -0,0 +1,2 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<problems/>

java/java-tests/testData/inspection/emptyMethod/superWithoutSync/src/p1/Base.java

@@ -0,0 +1,4 @@
+package p1;
+public class Base {
+  public void foo() {System.out.println("");}
+}

java/java-tests/testData/inspection/emptyMethod/superWithoutSync/src/p2/Derived.java

@@ -0,0 +1,7 @@
+package p2;
+import p1;
+public class Derived extends p1.Base {
+  public synchronized void foo() {
+     super.foo();
+  }
+}