Display marks using maxMarks rather than content

[sjd210]

See isaacphysics/isaac-api#722 (Don't merge yet!)

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 41.21%. Comparing base (d434c1f) to head (4a0c474).
⚠️ Report is 95 commits behind head on main.

Files with missing lines	Patch %	Lines
...pp/components/content/IsaacLLMFreeTextQuestion.tsx	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1704      +/-   ##
==========================================
- Coverage   41.21%   41.21%   -0.01%     
==========================================
  Files         529      529              
  Lines       23353    23354       +1     
  Branches     7725     6889     -836     
==========================================
  Hits         9626     9626              
- Misses      13094    13687     +593     
+ Partials      633       41     -592     

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[axlewin]

lgtm, pending a release