Fix notebook showing up in template when not selected (#743)

## Changes
This fixes a typo that caused the notebook.ipynb file to show up even if
the user answered "no" to the question about including a notebook.

## Tests
We have matrix validation tests for all the yes/no combinations and
whether the build + validate. There is no current test for the absence
of files.

libs/template/templates/default-python/template/__preamble.tmpl

@@ -28,7 +28,7 @@ This file only template directives; it is skipped for the actual output.
 {{end}}
 
 {{if $notNotebook}}
-  {{skip "{{.project_name}}/src/notebook.iypnb"}}
+  {{skip "{{.project_name}}/src/notebook.ipynb"}}
 {{end}}
 
 {{if (and $notDLT $notNotebook $notPython)}}