Fix subprimitive validation using primitive instead of class instance

[wyfo]

No description provided.

[codecov-commenter]

Codecov Report

Merging #345 (fb456b3) into master (1fb6687) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #345      +/-   ##
==========================================
+ Coverage   86.19%   86.22%   +0.02%     
==========================================
  Files          67       67              
  Lines        5889     5886       -3     
  Branches     1222     1221       -1     
==========================================
- Hits         5076     5075       -1     
+ Misses        594      593       -1     
+ Partials      219      218       -1     

Impacted Files	Coverage Δ
apischema/deserialization/__init__.py	99.65% <100.00%> (+0.66%)	⬆️

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