Enable feature for example custom_3d_glow

[Johnchoi913]

• Small fix, no issue opened
• [x] I have followed the instructions in the PR template

[github-actions[bot]]

Preview available at https://egui-pr-preview.github.io/pr/7730-example-custom-3d-glow-minor-fix Note that it might take a couple seconds for the update to show up after the preview_build workflow has completed.

View snapshot changes at kitdiff

[emilk]

Thanks!