Prettier - Move exclamation mark to outside the single quotes of flatpak-build

[ram1660]

This is my first pull request.

In Windows when you try to run yarn prettier or yarn prettier-fix the commands won't work because the ! is being inside the single quotes of the "flatpak-build" and there maybe be difference between Windows and Linux where Windows treats the '!flatpak-build' as a folder while we are trying to ignore the folder.
By moving the exclamation mark to the outside of the single quote you will be able to run prettier and ignore the "flatpak-build" folder.
I have tested this in Windows and WSL Ubuntu and the and it works on both of them.

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Use the following Checklist if you have changed something on the Backend or Frontend:

• Tested the feature and it's working on a current and clean install.
• Tested the main App features and they are still working on a current and clean install. (Login, Install, Play, Uninstall, Move games, etc.)
• Created / Updated Tests (If necessary)
• Created / Updated documentation (If necessary)

[arielj]

closing as it was replaced by #3219