Reduce number of iterations in USB tutorial

[atskae]

Fixes #2711

Description

Reduces the number of training iterations from 4,000 to 500, which now runs for 3 minutes with an accuracy of 87%.
Also fixes the broken image link on the USB framework.

Checklist

• The issue that is being fixed is referred in the description (see above "Fixes #ISSUE_NUMBER")
• Only one issue is addressed in this pull request
• Labels from the issue that this PR is fixing are added to this pull request
• No unnecessary issues are included into this pull request.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/tutorials/2771

• 📄 Preview Python docs built from this PR

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✅ No Failures

As of commit da46b62 with merge base 475671e ():
💚 Looks good so far! There are no failures yet. 💚

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[atskae]

I wrote out what SSL and ViT stood for (please double check) since they are used throughout the tutorial and initially I didn't know what they meant. Maybe for ML experts they are obvious...

[svekars]

cc: @Hhhhhhao

[atskae]

Should I be concerned with this warning?

/var/lib/jenkins/workspace/advanced/usb_semisup_learn.rst: WARNING: document isn't included in any toctree

[atskae]

Thanks for the initial comments! Hopefully I addressed the main issues, though I'm still not sure why CI is hanging/failing... As a newcomer I'd appreciate any help, thank you!

[atskae]

I can't seem to add @Hhhhhhao as a reviewer or add labels to the PR 😓

[atskae]

Run pyspelling
Misspelled words:
<url-free> beginner_source/colab.rst
--------------------------------------------------------------------------------
Nvidia
--------------------------------------------------------------------------------

!!!Spelling check failed!!!

How should I address this error? Do we make an exception or should I avoid using this word?

[atskae]

Thank you for your comments!

[atskae]

@Hhhhhhao Are there any other changes that I should make?

[Hhhhhhao]

@Hhhhhhao Are there any other changes that I should make?

I think that would be all for now. Thanks for the help!