Cleanup CI configuring composer's minimum-stability

[norkunas]

Pull Request

Related issue

Fixes #<issue_number>

What does this PR do?

• Removes a workaround in CI which allowed to test Symfony 7.3, which is not necessary anymore as it was generally released.

PR checklist

Please check if your PR fulfills the following requirements:

• Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
• Have you read the contributing guidelines?
• Have you made sure that the title is accurate and descriptive of the changes?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.41%. Comparing base (9f01002) to head (6dbf600).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #383   +/-   ##
=========================================
  Coverage     88.41%   88.41%           
  Complexity        1        1           
=========================================
  Files            20       20           
  Lines           889      889           
=========================================
  Hits            786      786           
  Misses          103      103           

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