rsvg_handle_get_dimensions is deprecated in 2.52.0

rsvg_handle_get_dimensions is deprecated in 2.52.0

In Bug#44655#32 (2020-11-19) it was reported that
rsvg_handle_get_dimensions was not deprecated.  However, it became
deprecated in librsvg 2.52.0 (2021-09-15), and because of this Emacs
builds with --enable-gcc-warnings fail in Fedora 35 (2025-11-02)
with the diagnostic “‘rsvg_handle_get_dimensions’ is deprecated:
Use 'rsvg_handle_get_intrinsic_size_in_pixels' instead
[-Werror=deprecated-declarations]”.
* src/image.c (rsvg_handle_get_dimensions): Define as a DLL
function only if < librsvg 2.46.0, since it’s not used
in 2.46.0 or later.
(svg_load_image): Use rsvg_handle_get_dimensions only if librsvg <
2.46.0, since it isn’t needed if >= 2.46.0.