I consider a shower ceiling as a damp, not wet, location and the fixture should be marked and listed as such.
While the NEC does not mandate GFCI protection for a light fixture above a shower, manufactures instructions may state otherwise.
The light must be listed for damp location or wet location if subject to shower spray. No gfci is needed unless the fixture manufacturer states it inside the can
Here is the code section we are talking about.
410.10(D) Bathtub and Shower Areas.
No parts of cord-connected luminaires, chain-, cable-, or
cord-suspended luminaires, lighting track, pendants, or ceiling-suspended (paddle)
fans shall be located within a zone measured 900 mm (3 ft)
horizontally and 2.5 m (8 ft) vertically from the top of the
bathtub rim or shower stall threshold. This zone is all encom-
passing and includes the space directly over the tub or shower
stall.
Luminaires located within the actual outside dimension
of the bathtub or shower to a height of 2.5 m (8 ft) vertically
from the top of the bathtub rim or shower threshold shall be
marked for damp locations, or marked for wet locations where
subject to shower spray