fix: Downgrade wicked_pdf to 2.6.3

[Quentinchampenois]

🎩 Description

Please describe your pull request.

Downgrade wicked_pdf to be compatible with Webpacker.
Add specs

📌 Related Issues

Link your PR to an issue

• Related to fix: downgrade wicked_pdf #458
• Related to version 2.7.0 breaks with webpacker  mileszs/wicked_pdf#1098
• Notion card

Testing

Describe the best way to test or validate your PR.

If you have a Running Docker env you can easily setup using : make run

Tasks

• Add specs
• Downgrade wicked_pdf

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f4ae434) 89.34% compared to head (d64a913) 89.34%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #477   +/-   ##
========================================
  Coverage    89.34%   89.34%           
========================================
  Files           65       65           
  Lines         1595     1595           
========================================
  Hits          1425     1425           
  Misses         170      170           

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