router change made one level of rpcenv mut superfluous

Created via `cargo fix`.  see commit
47acc8dc8f68ed2c5db69b1678b479e05b0a3194 from proxmox-rs

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

src/api2/tape/backup.rs

@@ -79,7 +79,7 @@ fn check_backup_permission(
 /// List all tape backup jobs
 pub fn list_tape_backup_jobs(
     _param: Value,
-    mut rpcenv: &mut dyn RpcEnvironment,
+    rpcenv: &mut dyn RpcEnvironment,
 ) -> Result<Vec<TapeBackupJobStatus>, Error> {
     let auth_id: Authid = rpcenv.get_auth_id().unwrap().parse()?;
     let user_info = CachedUserInfo::new()?;