Compile warnings in Elixir 1.17

I am getting a couple of runtime warnings like this one:
```
using map.field notation (without parentheses) to invoke function MyApp.Repo.__adapter__() is deprecated,
you must add parentheses instead: remote.function()
```

This refers to this code (which is used 7 times in `triplex.ex`):
```elixir
case repo.__adapter__ do
```

It would be nice to have this cleaned up.