Change nv cargo categories

To publish our crate, we must use official categories.  In this case,
"virtualization" specifically calls out containers and seems
appropriate.

Upstream: rust-lang/crates.io#8930

Signed-off-by: Brent Baude <bbaude@redhat.com>

Author: baude

Cargo.toml

@@ -8,7 +8,7 @@ readme = "README.md"
 description = "A container network stack"
 homepage = "https://github.com/containers/netavark"
 repository = "https://github.com/containers/netavark"
-categories = ["containers", "networking", "podman"]
+categories = ["virtualization"]
 exclude = ["/.cirrus.yml", "/.github/*", "/hack/*"]
 build = "build.rs"