Symbol Editor: Fix reverting changes on a root symbol: derived symbols are displayed wrong

Reverting changes broke links between derived symbols and the root symbol.
Now fixed by do not delete and recreate reverted symbol.
Fixes #10792
https://gitlab.com/kicad/code/kicad/issues/10792

eeschema/symbol_library_manager.cpp

@@ -528,7 +528,8 @@ LIB_ID SYMBOL_LIBRARY_MANAGER::RevertSymbol( const wxString& aAlias, const wxStr
     }
     else
     {
-        symbolBuf->SetSymbol( new LIB_SYMBOL( original ) );
+        // copy the initial data to the current symbol to restore
+        *symbolBuf->GetSymbol() = original;
         OnDataChanged();
     }