Bump PG versions to 17.7, 16.11, 15.15

[naisila]

Sister PR https://github.com/citusdata/the-process/pull/162

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 88.74%. Comparing base (62a9190) to head (6381c94). :warning: Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8355   +/-   ##
=======================================
  Coverage   88.74%   88.74%           
=======================================
  Files         287      287           
  Lines       63020    63020           
  Branches     7891     7891           
=======================================
  Hits        55925    55925           
- Misses       4777     4780    +3     
+ Partials     2318     2315    -3     

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