Florian Müllner authored Nov 10, 2023 and Marge Bot committed Nov 14, 2023

clutter_keyval_name() returns a pointer to a static array, not
newly allocated memory. Add a transfer annotation to indicate
that callers must not free the returned memory.

While add it, make the return value const to stress further that
callers shouldn't touch the returned memory.

Part-of: <!3386>