Removed the text "Warning" for Win64 from uplugin file

[RiotRampRoy]

Win64 was the only platform to have the "Warning" at the start of the message. Removing this brings it in line with messaging for the other platforms.

[github-actions]

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## Unreleased

- Removed the text "Warning" for Win64 from uplugin file ([#1084](https://github.com/getsentry/sentry-unreal/pull/1084))

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[tustanivsky]

Since we no longer have a separate FAB (UE Marketplace) plugin package without symbol upload scripts the check here can be removed entirely. However, since some of the related changes are already made in #1076 it’s fine to just update the message for now.