export_workspace doesn't work with a pipe in the notebook name on Windows

[znanfelt]

Steps to reproduce:

1. create notebook with a "|" character in it in Databricks via the website, for example: "/Shared/sub-folder/sample|notebook"
2. run the following command locally:

databricks workspace export_dir /Shared/ c:/temp/

3. Error occurs:

ERROR: OSError: [Errno 22] Invalid argument: 'c:/temp\sub-folder\sample|notebook.sql'