Old queries cleanup times out.

From demo Cloak:
client #PID<0.4267.0> timed out because it queued and checked out the connection for longer than 15000ms

#PID<0.4267.0> was at location:

    (stdlib 3.13.2) gen.erl:208: :gen.do_call/4
    (stdlib 3.13.2) gen_statem.erl:671: :gen_statem.call_dirty/4
    (ssl 10.1) ssl_connection.erl:2576: :ssl_connection.call/2
    (postgrex 0.15.7) lib/postgrex/protocol.ex:2838: Postgrex.Protocol.msg_recv/4
    (postgrex 0.15.7) lib/postgrex/protocol.ex:1880: Postgrex.Protocol.recv_bind/3
    (postgrex 0.15.7) lib/postgrex/protocol.ex:1772: Postgrex.Protocol.bind_execute/4
    (db_connection 2.3.0) lib/db_connection/holder.ex:316: DBConnection.Holder.holder_apply/4
    (db_connection 2.3.0) lib/db_connection.ex:1254: DBConnection.run_execute/5

2021-07-09 11:53:44.682 [air@demo-air-air] [error]: Task #PID<0.4267.0> started from #PID<0.2784.0> terminating
** (DBConnection.ConnectionError) ssl recv: closed (the connection was closed by the pool, possibly due to a timeout or because the pool has been terminated)
    (ecto_sql 3.5.3) lib/ecto/adapters/sql.ex:751: Ecto.Adapters.SQL.raise_sql_call_error/1
    (ecto_sql 3.5.3) lib/ecto/adapters/sql.ex:684: Ecto.Adapters.SQL.execute/5
    (air 21.2.0-lts) lib/air/service/cleanup.ex:16: Air.Service.Cleanup.cleanup_old_queries/2
    (elixir 1.11.1) lib/task/supervised.ex:90: Task.Supervised.invoke_mfa/2
    (stdlib 3.13.2) proc_lib.erl:226: :proc_lib.init_p_do_apply/3
Function: #Function<0.33537705/0 in Periodic.start_job/1>
    Args: []
Aircloak / aircloak

Old queries cleanup times out. #4944
