[fix](histogram) Fix histgrom nullable properties on branch-2.1 (#40638)

nullable property of histogram on master is changed by
#37330
pick it to branch-2.1
related change on 2.1: #38608,
#38608 relies on AlwaysNotNullable property.

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/agg/Histogram.java

@@ -19,8 +19,8 @@
 
 import org.apache.doris.catalog.FunctionSignature;
 import org.apache.doris.nereids.trees.expressions.Expression;
+import org.apache.doris.nereids.trees.expressions.functions.AlwaysNotNullable;
 import org.apache.doris.nereids.trees.expressions.functions.ExplicitlyCastableSignature;
-import org.apache.doris.nereids.trees.expressions.functions.PropagateNullable;
 import org.apache.doris.nereids.trees.expressions.functions.SearchSignature;
 import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
 import org.apache.doris.nereids.types.DoubleType;
@@ -37,7 +37,7 @@
  * AggregateFunction 'histogram'. This class is generated by GenerateFunction.
  */
 public class Histogram extends AggregateFunction
-        implements ExplicitlyCastableSignature, PropagateNullable {
+        implements ExplicitlyCastableSignature, AlwaysNotNullable {
 
     public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
             FunctionSignature.ret(VarcharType.SYSTEM_DEFAULT)