Fix destination constraint view displaying over other controls

[egfx-notifications]

There was already a fix in place for Mono, this commit generalizes the fix (and removes the explicit Mono handling - I have not yet checked how it looks in Mono now, but I think this should be fine).

Fixes https://github.com/dlech/KeeAgent/issues/351

[ChristianGfK]

Checked on Windows with 2.52 and no UI scaling in place, makes no visible difference. (That is, no negative impact.)

[dlech]

Thanks!