[java] change access modifier of RemoteWebElement.execute method (#8398)

We have extended RemoteWebElement and added more capabilities by extending RemoteWebElement. We have overridden `execute` method.

Now this method has been replaced by `CommandPayload` arguments, these need to be a protected method to support override. Earlier it was support in selenium version 2 and 3.

java/client/src/org/openqa/selenium/remote/RemoteWebElement.java

@@ -232,7 +232,7 @@ protected List<WebElement> findElements(String using, String value) {
     return allElements;
   }
 
-  Response execute(CommandPayload payload) {
+  protected Response execute(CommandPayload payload) {
     return parent.execute(payload);
   }