The pkgconf build dependency is unused.

The Meson build does not execute pkg-config/pkgconf or use it for
dependency discovery. The microdns.pc file is generated directly from
src/microdns.pc.in using Meson's configure_file().

I rebuilt the package in a clean Debian unstable container without
pkgconf or pkgconf-bin. The build completed successfully, the unit test
passed, and microdns.pc was still generated and installed.

The attached patch removes pkgconf from Build-Depends.

The patch is based on the current Salsa master. vcswatch currently
reports that the Salsa repository is not synchronized with the uploaded
package.