Enhancement: Raise error level from 5 to 4

[localheinz]

This PR

• raises the error level for vimeo/psalm from 5 to 4
• fixes issues reported via static code analysis

Follows #1897.

[codecov-io]

Codecov Report

Merging #2084 into next will increase coverage by 0.12%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##               next    #2084      +/-   ##
============================================
+ Coverage     70.82%   70.95%   +0.12%     
  Complexity     1599     1599              
============================================
  Files           287      287              
  Lines          3863     3863              
============================================
+ Hits           2736     2741       +5     
+ Misses         1127     1122       -5     

Impacted Files	Coverage Δ	Complexity Δ
src/Faker/Provider/ms_MY/Address.php	94.33% <ø> (+3.77%)	13.00 <0.00> (ø)
src/Faker/Provider/ms_MY/Miscellaneous.php	0.00% <ø> (ø)	7.00 <0.00> (ø)
src/Faker/Provider/ms_MY/Payment.php	0.00% <ø> (ø)	8.00 <0.00> (ø)
src/Faker/Provider/de_AT/Person.php	0.00% <0.00%> (-100.00%)	1.00% <0.00%> (ø%)
src/Faker/Provider/es_AR/Person.php	0.00% <0.00%> (-100.00%)	1.00% <0.00%> (ø%)
src/Faker/Provider/ne_NP/Person.php	0.00% <0.00%> (-50.00%)	2.00% <0.00%> (ø%)
src/Faker/Provider/id_ID/Company.php	50.00% <0.00%> (-50.00%)	2.00% <0.00%> (ø%)
src/Faker/Provider/sv_SE/Address.php	50.00% <0.00%> (-50.00%)	4.00% <0.00%> (ø%)
src/Faker/Provider/en_AU/PhoneNumber.php	0.00% <0.00%> (-50.00%)	2.00% <0.00%> (ø%)
src/Faker/Provider/ro_MD/Address.php	65.21% <0.00%> (-34.79%)	10.00% <0.00%> (ø%)
... and 37 more

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