Remove redundant Region::copyFrom()

We already have an assignment operator, so no need for this method.
diff --git a/common/rfb/EncodeManager.cxx b/common/rfb/EncodeManager.cxx
index 4f6ad5a..0ceec8f 100644
--- a/common/rfb/EncodeManager.cxx
+++ b/common/rfb/EncodeManager.cxx
@@ -255,7 +255,7 @@
 
     prepareEncoders();
 
-    changed.copyFrom(ui.changed);
+    changed = ui.changed;
 
     /*
      * We need to render the cursor seperately as it has its own