Drop unused pydantic[email] extra from palace-opds (#3246)

## Description

`palace-opds`'s `pyproject.toml` declared `pydantic[email]` but nothing
in the package uses `EmailStr` / `email_validator` — the only email
field (the LCP license owner email in `palace.opds.lcp.license`) is a
plain `str`. Drop the extra so anyone installing `palace-opds`
standalone doesn't pull in `email-validator` and its transitive deps.

## How Has This Been Tested?

- `uv lock` — only the palace-opds edge changed; no other resolution
churn.
- `mypy` passes.
- `pytest tests/palace_opds` — 174 tests pass.

## Checklist

- [x] I have updated the documentation accordingly.
- [x] All new and existing tests passed.

Author: jonathangreen

packages/palace-opds/pyproject.toml

@@ -7,7 +7,7 @@ authors = [{name = "The Palace Project", email = "info@thepalaceproject.org"}]
 dependencies = [
     "palace-util",
     "pycountry>=26.2.16,<27",
-    "pydantic[email]>=2.12,<3",
+    "pydantic>=2.12,<3",
     "uritemplate==4.2.0",
 ]
 description = "Pydantic models for OPDS 2.0, RWPM, ODL, LCP, and Palace Project extensions."