[frameit] fix the screenshot size of iPhone 8 Plus

[yunhao]

Checklist

• I've run bundle exec rspec from the root directory to see all new and existing tests pass
• I've followed the fastlane code style and run bundle exec rubocop -a to ensure the code style is valid
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.

Motivation and Context

#17976

Description

In the previous version of fastlane, frameit can not frame a iPhone 8 Plus screenshot. Because the correct image size is 1242 x 2208, which is incorrectly specified as 1080 x 1920.

Testing Steps

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[yunhao]

@googlebot I signed it!

[ainame]

👍

I'm just curious about how you got the error you mentioned in the original issue but this PR just looks right.
#17976 (comment)

Thank you and congrats your first-time contribution! 🎉
@joshdholtz will then double-check and merge this when he can 🙇

[joshdholtz]

This looks good to me! Thanks for fixing this 😊

[fastlane-bot]

Congratulations! 🎉 This was released as part of fastlane 2.172.0 🚀