build: do not search for unused sqlite header

This was necessary to ensure compilation with Visual Studio's cl.exe on
conda-forge (see https://github.com/conda-forge/staged-recipes/pull/12226).
1 job for master in 2 minutes and 2 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #839316
ipv6
fedora-meson-x86_64

00:02:02