gpui: Fix typo in Windows alpha correction shader (#37328)

This PR fixes a typo in the Windows alpha correction shader that is now
caught by https://github.com/zed-industries/zed/pull/37314.

Another case that could be addressed by Bors.

Release Notes:

- N/A
965dbc988fMarshall Bowers committed on 9/1/2025, 7:33:11 PM· committed by GitHubparent5b73b40
1 file changedLine totals unavailable