docs: update required meson version

Fixes: f7b6a8d1 ("meson: bump required version to 0.46")
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
13 jobs for !1495 with meson-docs-0.46
detached
Status Name Job ID Coverage
  Containers Build
canceled debian #461209

 
  Build+Test
skipped meson-arm64 #461218
skipped meson-armhf #461217
skipped meson-clang #461211
skipped meson-clover #461215
skipped meson-i386 #461219
skipped meson-main #461214
skipped meson-swr-glvnd #461210
skipped meson-vulkan #461216
skipped scons-llvm #461221
skipped scons-nollvm #461220
skipped scons-swr #461212
skipped scons-win64 #461213