Update PostgreSQL version in tests and CI

[mfvanek]

Relates to mfvanek/pg-index-health#618

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.81%. Comparing base (59026d0) to head (4c1b347).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #259   +/-   ##
=========================================
  Coverage     90.81%   90.81%           
  Complexity       59       59           
=========================================
  Files            25       25           
  Lines           185      185           
  Branches          6        6           
=========================================
  Hits            168      168           
  Misses           14       14           
  Partials          3        3           

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