Docs fix: add tutorial download image

[CamStan]

Description

The tutorial download image for the slides did not come through in the original PR. Trying again.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Performance enhancement (non-breaking change which improves efficiency)
• [ ] Code cleanup (non-breaking change which makes code smaller or more readable)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Testing (addition of new tests or update to current tests)
• [x] Documentation (a change to man pages or other documentation)

Checklist:

• [x] My code follows the UnifyFS code style requirements.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.
• [x] All commit messages are properly formatted.

[CamStan]

@adammoody, the image for downloading the tutorial slides didn't come through in the original PR for some reason. This should fix it.

Checkpatch is failing because a diff can't be produced. You can ignore that.

[adammoody]

Thanks, @CamStan .