Update base.fs.upload docs to reflect exceptions thrown

[eelkevdbos]

Type of changes

• Documentation / docstrings

Checklist

• I've run the latest black with default args on new code.
• I've updated CHANGELOG.md and CONTRIBUTORS.md where appropriate.
• I've added tests for new code.
• I accept that @PyFilesystem/maintainers may be pedantic in the code review.

Description

A small docs improvement I came across while using the fs.base.upload method. It reflects the method throwing ResourceNotFound if the path you are uploading to does not exist.

[althonos]

Thanks for the PR @eelkevdbos !

Could you possibly add a test to reflect this to fs.test? If this is an explicitly advertised behaviour then we need to check all filesystems behave so.

[althonos]

Thanks a bunch!