update summary tag

Author: Becca McHenry

src/Microsoft.ML.AutoML/API/AutoMLExperimentExtension.cs

@@ -258,9 +258,11 @@ public static AutoMLExperiment SetGridSearchTuner(this AutoMLExperiment experime
             return experiment;
         }
 
+        /// <summary>
         /// Set checkpoint folder for <see cref="AutoMLExperiment"/>. The checkpoint folder will be used to save
         /// temporary output, run history and many other stuff which will be used for restoring training process 
         /// from last checkpoint and continue training.
+        /// </summary>
         /// <param name="experiment"><see cref="AutoMLExperiment"/>.</param>
         /// <param name="folder">checkpoint folder. This folder will be created if not exist.</param>
         /// <returns><see cref="AutoMLExperiment"/></returns>