Drop redundant param from WindowFunctionDefinition::return_field

It became redundant when `input_expr_types: &[DataType]` was replaced
with `input_expr_fields: &[Field]`, i.e. in
577c424 commit. The benefit of passing
in a "field" is that it combines data type and nullable attribute.

Author: findepi

datafusion/expr/src/expr.rs

@@ -1039,7 +1039,6 @@ impl WindowFunctionDefinition {
     pub fn return_field(
         &self,
         input_expr_fields: &[FieldRef],
-        _input_expr_nullable: &[bool],
         display_name: &str,
     ) -> Result<FieldRef> {
         match self {

datafusion/physical-plan/src/windows/mod.rs

@@ -69,12 +69,7 @@ pub fn schema_add_window_field(
         .iter()
         .map(|e| Arc::clone(e).as_ref().return_field(schema))
         .collect::<Result<Vec<_>>>()?;
-    let nullability = args
-        .iter()
-        .map(|e| Arc::clone(e).as_ref().nullable(schema))
-        .collect::<Result<Vec<_>>>()?;
-    let window_expr_return_field =
-        window_fn.return_field(&fields, &nullability, fn_name)?;
+    let window_expr_return_field = window_fn.return_field(&fields, fn_name)?;
     let mut window_fields = schema
         .fields()
         .iter()