grid-cell, name-cell: Revert emblem workaround
This reverts commit 032d7d00. Since GTK 4.11.2, the workaround in that commit is not needed anymore, as gtk@e20a5e1b fixes the lookup behavior for unthemed icons. See gtk!5865 (merged) for more details. GTK 4.11.2 is the required version already in meson.build, so the fix should be included.