💥 Remove builtin postgres adapter

[Fs02]

• This adapter has been moved to github.com/go-rel/postgres (https://github.com/go-rel/postgres)

[codecov]

Codecov Report

Merging #255 (33423fb) into master (48832cd) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #255   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           56        55    -1     
  Lines         3974      3884   -90     
=========================================
- Hits          3974      3884   -90     

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