[fix](nereids)use equals instead of == to compare String (apache#45628)

when comparing column name, we should use equals method instead of '=='
to compare the content

fe/fe-core/src/main/java/org/apache/doris/nereids/rules/analysis/BindRelation.java

@@ -257,7 +257,7 @@ private LogicalPlan preAggForRandomDistribution(LogicalOlapScan olapScan) {
             SlotReference slot = SlotReference.fromColumn(olapTable, col, col.getName(), olapScan.qualified());
             ExprId exprId = slot.getExprId();
             for (Slot childSlot : childOutputSlots) {
-                if (childSlot instanceof SlotReference && ((SlotReference) childSlot).getName() == col.getName()) {
+                if (childSlot instanceof SlotReference && ((SlotReference) childSlot).getName().equals(col.getName())) {
                     exprId = childSlot.getExprId();
                     slot = slot.withExprId(exprId);
                     break;