Fix fuzzer deserialisation of newtype-like ron::value::RawValue

[juntyr]

Fix fuzzer-found issue #61688

* [ ] I've included my change in CHANGELOG.md

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.12% ⚠️

Comparison is base (3f877c2) 82.95% compared to head (ce26f6b) 82.83%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #484      +/-   ##
==========================================
- Coverage   82.95%   82.83%   -0.12%     
==========================================
  Files          74       74              
  Lines        9267     9281      +14     
==========================================
+ Hits         7687     7688       +1     
- Misses       1580     1593      +13     

Files Changed	Coverage Δ
src/value/raw.rs	81.16% <ø> (-7.49%)	⬇️
tests/407_raw_value.rs	99.48% <100.00%> (+<0.01%)	⬆️

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