go.mod: upgrade nfpm to v2 (#8786)

Upgrade the nfpm package to the latest version to pick up
https://github.com/goreleaser/nfpm/commit/24a43c5ad7cfc549e8a4ec930521a97a30f26cc8.
The upgrade is from v0 to v2, so there was some breakage to fix.
Generated packages should have the same contents as before.

Updates https://github.com/tailscale/tailscale/issues/1882

Signed-off-by: Andrew Lytvynov <awly@tailscale.com>

release/dist/unixpkgs/targets.go

@@ -11,8 +11,8 @@ import (
 
 	"tailscale.com/release/dist"
 
-	_ "github.com/goreleaser/nfpm/deb"
-	_ "github.com/goreleaser/nfpm/rpm"
+	_ "github.com/goreleaser/nfpm/v2/deb"
+	_ "github.com/goreleaser/nfpm/v2/rpm"
 )
 
 func Targets(signer crypto.Signer) []dist.Target {