revert useless code

Signed-off-by: Lantao Jin <ltjin@amazon.com>

Author: LantaoJin

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

@@ -135,7 +135,6 @@ public RexNode visitLiteral(Literal node, CalcitePlanContext context) {
             new BigDecimal(Double.toString((Double) value)),
             typeFactory.createSqlType(SqlTypeName.DOUBLE));
       case DECIMAL:
-        int sc = ((BigDecimal) value).scale();
         return rexBuilder.makeExactLiteral((BigDecimal) value);
       case BOOLEAN:
         return rexBuilder.makeLiteral((Boolean) value);