remove an unused `app` var in cli.py

this var isn't actually used? unless init it does some side-effect outside of the event loop, idon't think it's necessary. 

Feel free to ignore this PR if the deleted line actually does something.

datasette/cli.py

@@ -180,7 +180,6 @@ def inspect(files, inspect_file, sqlite_extensions):
     This can then be passed to "datasette --inspect-file" to speed up count
     operations against immutable database files.
     """
-    app = Datasette([], immutables=files, sqlite_extensions=sqlite_extensions)
     loop = asyncio.get_event_loop()
     inspect_data = loop.run_until_complete(inspect_(files, sqlite_extensions))
     if inspect_file == "-":