Update to sample preventing adding and publishing error

[jyaistMap]

• sample notebook updating_features_in_a_feature_layer was failing to add item because the csv file backing the item already exists for the arcgis_python user.
  • added cell to create a copy of the original capitals_1.csv file so users trying it live can add an item to the portal with the current time appended to the file name as well as the published layer (before renaming)
  • also removed the colon from the title of the examining_item_thumbnail_size because it caused error internally

[AtmaMani]

thanks @jyaistMap