chore(data/zmod/algebra): make zmod.algebra a def (#19197)
`zmod.algebra` creates a diamond about the `zmod p`-algebra structure on `zmod p`:
```lean
import algebra.algebra.basic
import data.zmod.algebra
example (p : ℕ) : algebra.id (zmod p) =
(zmod.algebra (zmod p) p) := rfl --fails
```
This is also causing troubles with the port. We turn `zmod.algebra` into a def.
