Revert "build: Require Meson >= 0.50"

This reverts commit 17777040.

Some projects that include Tracker haven't yet updated to Meson 0.50. This
change broke gnome-build-meta for example:
https://gitlab.gnome.org/GNOME/gnome-build-meta/-/jobs/286671

The install: arg isn't actually required as for configure_file() targets
Meson will infer whether an install is needed by the presence of the
install_dir: arg.
1 job for master in 2 minutes and 15 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #287059
test-fedora-latest

00:02:15