x11/lavalauncher: unbreak with LIBRSVG2_DEFAULT=legacy

meson.build:53:0: ERROR: Invalid version of dependency, need 'librsvg-2.0' ['>= 2.45.6'] found '2.40.21'.

Reported by: pkg-fallout (riscv64)

(cherry picked from commit 4e8b070e2129e81b2faaf30ca2fa782a20308d92)