fix warning in Elixir 1.19

[woylie]

Fixes this warning:

    warning: a struct for Ecto.Changeset is expected on struct update:

        %Ecto.Changeset{
          changeset
          | action: parent_action,
            params: params,
            errors: errors,
            valid?: errors == []
        }

    but got type:

        dynamic()

    where "changeset" was given the type:

        # type: dynamic()
        # from: lib/polymorphic_embed/html/helpers.ex:76:19
        changeset =
          apply_action(
            Ecto.Changeset.change(data),
            parent_action
          )

    when defining the variable "changeset", you must also pattern match on "%Ecto.Changeset{}".

    hint: given pattern matching is enough to catch typing errors, you may optionally convert the struct update into a map update. For example, instead of:

        user = some_function()
        %User{user | name: "John Doe"}

    it is enough to write:

        %User{} = user = some_function()
        %{user | name: "John Doe"}

    typing violation found at:
    │
 83 │         changeset = %Ecto.Changeset{
    │                     ~
    │
    └─ lib/polymorphic_embed/html/helpers.ex:83:21: PolymorphicEmbed.HTML.Helpers.to_form/4

[coveralls]

Pull Request Test Coverage Report for Build ebe5ef0a22737e3b000ea256383255c9591cfa49-PR-140

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 82.933%

---

Totals
Change from base Build 17b5c7687076b7b199108b76e0de4a6b5e337959:	0.0%
Covered Lines:	311
Relevant Lines:	375

---

💛 - Coveralls

[mathieuprog]

Released in 5.0.6