Fix typo

Author: dongjoon-hyun

Sources/SparkConnect/DataFrame.swift

@@ -735,15 +735,15 @@ public actor DataFrame: Sendable {
 
   /// Groups the ``DataFrame`` using the specified columns, so we can run aggregation on them.
   /// - Parameter cols: Grouping column names.
-  /// - Returns:A ``GroupData``.
+  /// - Returns:A ``GroupedData``.
   public func groupBy(_ cols: String...) -> GroupedData {
     return GroupedData(self, GroupType.groupby, cols)
   }
 
   /// Create a multi-dimensional rollup for the current Dataset using the specified columns, so we
   /// can run aggregation on them.
   /// - Parameter cols: Grouping column names.
-  /// - Returns:A ``GroupData``.
+  /// - Returns:A ``GroupedData``.
   public func rollup(_ cols: String...) -> GroupedData {
     return GroupedData(self, GroupType.rollup, cols)
   }
@@ -752,7 +752,7 @@ public actor DataFrame: Sendable {
   /// can run aggregation on them. See [[RelationalGroupedDataset]] for all the available aggregate
   /// functions.
   /// - Parameter cols: Grouping column names.
-  /// - Returns:A ``GroupData``.
+  /// - Returns:A ``GroupedData``.
   public func cube(_ cols: String...) -> GroupedData {
     return GroupedData(self, GroupType.cube, cols)
   }