scripts/install: add Alma Linux.

Tested using an Alma Linux 8.5 VM.
Updates https://github.com/tailscale/tailscale/issues/2915

Signed-off-by: Denton Gentry <dgentry@tailscale.com>

scripts/installer.sh

@@ -151,7 +151,7 @@ main() {
 				VERSION=""
 				PACKAGETYPE="dnf"
 				;;
-			rocky)
+			rocky|almalinux)
 				OS="fedora"
 				VERSION=""
 				PACKAGETYPE="dnf"