chore: use or/2 over ||/2

Reason for that is that `a || b` will expand to:

```
case a do
  val when val in [false, nil] -> b
  val -> val
end
```

Which is harder to optimise by the compiler. `or/2` works only with
booleans, so in places where we do not care about returned value or
`nil` cases, it is better to use `or/2`.

lib/supavisor/client_handler.ex

@@ -297,7 +297,7 @@ defmodule Supavisor.ClientHandler do
              Cachex.get(Supavisor.Cache, key) == {:ok, nil} do
           case auth_secrets(info, data.user, key, 15_000) do
             {:ok, {method2, secrets2}} = value ->
-              if method != method2 || Map.delete(secrets.(), :client_key) != secrets2.() do
+              if method != method2 or Map.delete(secrets.(), :client_key) != secrets2.() do
                 Logger.warning("ClientHandler: Update secrets and terminate pool")
 
                 Cachex.update(
@@ -632,7 +632,7 @@ defmodule Supavisor.ClientHandler do
     db_info =
       case Db.get_state_and_mode(pid) do
         {:ok, {state, mode} = resp} ->
-          if state == :busy || mode == :session, do: Db.stop(pid)
+          if state == :busy or mode == :session, do: Db.stop(pid)
           resp
 
         error ->

lib/supavisor/db_handler.ex

@@ -451,7 +451,7 @@ defmodule Supavisor.DbHandler do
       )
     end
 
-    if state == :busy || data.mode == :session do
+    if state == :busy or data.mode == :session do
       :ok = sock_send(data.sock, <<?X, 4::32>>)
       :gen_tcp.close(elem(data.sock, 1))
       {:stop, {:client_handler_down, data.mode}}