Changes moderation category scores from float32 to float64

[johnyojohn]

Describe the change
Changes the types for moderation category scores from float32 to float64. This is because the openai api can return more significant digits than can be expressed in float32. In addition, the official openai go client uses float64 for moderation category scores (https://github.com/openai/openai-go/blob/main/moderation.go). Finally, the go's default JSON unmarshalling behavior for numbers is to store them into float64. I think these are all good reasons to change to float64.

Provide OpenAI documentation link
(https://platform.openai.com/docs/api-reference/moderations/create)

Describe your solution
Simply replacing the float32 types with float64.

Tests
N/A since float32 can be cast into float64 without losing precision.

Additional context

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.77%. Comparing base (ff9d83a) to head (5c5c2c0).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1018   +/-   ##
=======================================
  Coverage   85.77%   85.77%           
=======================================
  Files          43       43           
  Lines        2291     2291           
=======================================
  Hits         1965     1965           
  Misses        304      304           
  Partials       22       22           

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