Fix error.

Author: afoucret

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/ExpressionWritables.java

@@ -8,6 +8,7 @@
 package org.elasticsearch.xpack.esql.expression;
 
 import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
+import org.elasticsearch.xpack.esql.action.EsqlCapabilities;
 import org.elasticsearch.xpack.esql.core.expression.ExpressionCoreWritables;
 import org.elasticsearch.xpack.esql.expression.function.UnsupportedAttribute;
 import org.elasticsearch.xpack.esql.expression.function.aggregate.AggregateWritables;