Fix for #4055: Added testAssertStringNotEqualsFileCanonicalizing

[alecsmrekar]

In AssertTest.php I have added a function that tests assertStringNotEqualsFileCanonicalizing() by comparing the contents of a test xml file with some test strings.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (67cfab0) 89.34% compared to head (7fdb209) 89.37%.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #4645      +/-   ##
============================================
+ Coverage     89.34%   89.37%   +0.02%     
  Complexity     6425     6425              
============================================
  Files           683      683              
  Lines         20405    20405              
============================================
+ Hits          18230    18236       +6     
+ Misses         2175     2169       -6     

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[sebastianbergmann]

Cherry-picked into 10.5, will merge to main from there. Thanks!