stop using utils

Signed-off-by: Jialiang Liang <jiallian@amazon.com>

Author: RyanL1997

core/src/main/java/org/opensearch/sql/calcite/CalciteRelNodeVisitor.java

@@ -118,7 +118,7 @@
 import org.opensearch.sql.common.utils.StringUtils;
 import org.opensearch.sql.exception.CalciteUnsupportedException;
 import org.opensearch.sql.exception.SemanticCheckException;
-import org.opensearch.sql.expression.parse.RegexCommonUtils;
+import org.opensearch.sql.expression.parse.RegexExpression;
 import org.opensearch.sql.expression.function.BuiltinFunctionName;
 import org.opensearch.sql.expression.function.PPLFuncImpTable;
 import org.opensearch.sql.utils.ParseUtils;
@@ -179,7 +179,7 @@ public RelNode visitRex(Rex node, CalcitePlanContext context) {
 
     RexNode fieldRex = rexVisitor.analyze(node.getField(), context);
     String patternStr = (String) node.getPattern().getValue();
-    List<String> namedGroups = RegexCommonUtils.getNamedGroupCandidates(patternStr);
+    List<String> namedGroups = RegexExpression.getNamedGroupCandidates(patternStr);
 
     if (namedGroups.isEmpty()) {
       throw new IllegalArgumentException("Rex pattern must contain at least one named capture group");