Fix Coalesce optimizer. (#3955)

Author: Tony-Romanov

ydb/library/yql/core/peephole_opt/yql_opt_peephole_physical.cpp

@@ -8032,9 +8032,6 @@ TExprNode::TPtr OptimizeCoalesce(const TExprNode::TPtr& node, TExprContext& ctx)
     } else if (input.IsCallable("Nothing")) {
         YQL_CLOG(DEBUG, CorePeepHole) << "Drop " << node->Content() << " over " << input.Content();
         return node->TailPtr();
-    } else if (input.IsCallable("Just")) {
-        YQL_CLOG(DEBUG, CorePeepHole) << "Drop " << node->Content() << " over " << input.Content();
-        return node->HeadPtr();
     }
     return node;
 }