[core] Cleanup some tests.

[siad007]

Added return type hints and removed/changed the requirements annotations.

[codecov]

Codecov Report

Merging #1587 (e665d17) into main (1152fcf) will increase coverage by 0.16%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##               main    #1587      +/-   ##
============================================
+ Coverage     56.21%   56.38%   +0.16%     
  Complexity     6915     6915              
============================================
  Files           354      354              
  Lines         16744    16744              
============================================
+ Hits           9413     9441      +28     
+ Misses         7331     7303      -28     

Impacted Files	Coverage Δ	Complexity Δ
src/Phing/Task/System/Pdo/PDOSQLExecTask.php	53.14% <0.00%> (+8.57%)	75.00% <0.00%> (ø%)
src/Phing/Task/System/Pdo/PDOTask.php	62.79% <0.00%> (+30.23%)	18.00% <0.00%> (ø%)

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