feat(tutorial): use tutorial asset for block images

[tnagorra]

Changes

• use tutorial asset for block image

This PR doesn't introduce any:

• temporary files, auto-generated files or secret keys
• n+1 queries
• flake8 issues
• print
• typos
• unwanted comments

This PR contains valid:

• tests
• permission checks (tests here too)
• translations

[codecov]

Codecov Report

❌ Patch coverage is 93.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.68%. Comparing base (deec09b) to head (5e145f6).
⚠️ Report is 4 commits behind head on develop.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
apps/tutorial/models.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #87      +/-   ##
===========================================
+ Coverage    81.67%   81.68%   +0.01%     
===========================================
  Files          145      145              
  Lines         6040     6045       +5     
  Branches       523      523              
===========================================
+ Hits          4933     4938       +5     
  Misses         931      931              
  Partials       176      176              

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