ci(psalm): set up the minimum supported php version

[st3iny]

Upstream fix at nextcloud/.github#461

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 42.50%. Comparing base (2c5ec32) to head (f98a849).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #1581   +/-   ##
=========================================
  Coverage     42.50%   42.50%           
  Complexity      102      102           
=========================================
  Files            19       19           
  Lines           327      327           
=========================================
  Hits            139      139           
  Misses          188      188           

Flag	Coverage Δ
unittests	42.50% <ø> (ø)

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