Reactivate 12 skipped tests on PHP 7.4

[Seb35]

This was deactivated in 670487bd3214 but it works now (at least when tested locally on MW 1.35 + SMW master + SRF master). I guess the version of PHPUnit changed and/or the tests in SMW were improved.

[codecov-commenter]

Codecov Report

Merging #736 (ba87e5f) into master (84cace7) will increase coverage by 0.24%. The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #736      +/-   ##
============================================
+ Coverage     39.32%   39.57%   +0.24%     
  Complexity     2046     2046              
============================================
  Files            75       75              
  Lines          7234     7234              
============================================
+ Hits           2845     2863      +18     
+ Misses         4389     4371      -18     

Impacted Files	Coverage Δ
src/vCard/vCardFileExportPrinter.php	71.14% <0.00%> (+6.96%)	:arrow_up:
src/BibTex/BibTexFileExportPrinter.php	92.72% <0.00%> (+7.27%)	:arrow_up:

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