gpui: Revert `reuse_prepaint` change of #40767 (#41025)

https://github.com/zed-industries/zed/pull/40767/files/c95ae84d919462393455d858836f479dd24bd620#r2455674159
Release Notes:

- N/A *or* Added/Fixed/Improved ...
a66098b485Lukas Wirth committed on 10/23/2025, 4:23:35 PM· committed by GitHubparentb519ab2
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