fix: remove pydantic validation for rpc calls

[J0]

What kind of change does this PR introduce?

Currently, there is validation on /rpc calls which don't return responses in the conventional

{
  data: ...
}

format. This causes validation to fail and an error to be throw.

Current fix is hacky - open to suggestions on cleaner ways to fix this

Aims to fix: supabase/supabase-py#405 and #200

Manually tested - briefly converting to draft so I can write a test

[codecov]

Codecov Report

Patch coverage: 25.00% and project coverage change: -0.90% ⚠️

Comparison is base (3329234) 91.56% compared to head (3853dc1) 90.66%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #308      +/-   ##
==========================================
- Coverage   91.56%   90.66%   -0.90%     
==========================================
  Files          24       24              
  Lines        1197     1211      +14     
==========================================
+ Hits         1096     1098       +2     
- Misses        101      113      +12     

Files Changed	Coverage Δ
postgrest/_async/request_builder.py	75.45% <25.00%> (-4.16%)	⬇️
postgrest/_sync/request_builder.py	81.81% <25.00%> (-4.59%)	⬇️

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[J0]

Let's use #309