Update comments in flopy3boundaries.ipynb
Update comments in flopy3boundaries.ipynb

There were missing some commas in the comments of stress periods parameters.
Now the number of array elements consists with the documentation.
mrustl/flopy,jentjr/flopy,aleaf/flopy,jentjr/flopy,brclark-usgs/flopy,brclark-usgs/flopy,bdestombe/flopy-1,aleaf/flopy