Fixed UnixTimeGenerator collisions

[vudaltsov]

Description

See symfony/symfony#52367

Motivation and context

Closes #518

How has this been tested?

Manually via script in #518 (comment).

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

PR checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING.md document.
• I have added tests to cover my changes.

[codecov]

Codecov Report

Merging #522 (423313a) into 4.x (cc15557) will not change coverage.
Report is 1 commits behind head on 4.x.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##                4.x     #522   +/-   ##
=========================================
  Coverage     95.64%   95.64%           
  Complexity      584      584           
=========================================
  Files            70       70           
  Lines          1561     1561           
=========================================
  Hits           1493     1493           
  Misses           68       68           

Files	Coverage Δ
src/Generator/UnixTimeGenerator.php	97.82% <100.00%> (ø)

[ramsey]

Thank you for reporting this issue and helping to resolve it!