Switch to a different method of resolving ForwardRefs during deserialization for python 3.10.2 compatibility

[JWCook]

Closes #501

[codecov-commenter]

Codecov Report

Merging #503 (4c8e386) into master (0b8f7c8) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #503   +/-   ##
=======================================
  Coverage   98.76%   98.76%           
=======================================
  Files          18       18           
  Lines        1293     1293           
  Branches      187      187           
=======================================
  Hits         1277     1277           
  Misses          8        8           
  Partials        8        8           

Impacted Files	Coverage Δ
requests_cache/serializers/cattrs.py	92.85% <100.00%> (ø)

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