Fix support of typing.Any in GraphQL schema

[wyfo]

Fix #316

[codecov-commenter]

Codecov Report

Merging #317 (87b141f) into master (36b1b95) will increase coverage by 0.05%.
The diff coverage is 91.66%.

@@            Coverage Diff             @@
##           master     #317      +/-   ##
==========================================
+ Coverage   86.00%   86.05%   +0.05%     
==========================================
  Files          67       67              
  Lines        5888     5888              
  Branches     1225     1224       -1     
==========================================
+ Hits         5064     5067       +3     
+ Misses        602      600       -2     
+ Partials      222      221       -1     

Impacted Files	Coverage Δ
apischema/graphql/resolvers.py	84.96% <ø> (-0.20%)	⬇️
apischema/graphql/schema.py	86.87% <80.00%> (+0.80%)	⬆️
apischema/deserialization/methods.py	84.72% <100.00%> (-0.09%)	⬇️

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[wyfo]

I've just realized that Any translation in GraphQL schema was implemented too quickly, and there was in fact a "bug", because it should be JSON and not JSON!. So I would like to fix that too in this PR.
@thomascobb Is this change an issue for you? I will wait your answer before merging, or merge it monday evening otherwise.

[thomascobb]

That shouldn't be an issue, thanks