Drop Context from allowed types of template render method

[DEP 182](https://github.com/django/deps/blob/main/final/0182-multiple-template-engines.rst#backends-api)
states: "If `context` is provided, it must be a `dict`.".

While the `Jinja2` and `TemplateStrings` backends support arbitrary
mappings, `DjangoTemplates` calls `make_context()`, which only
supports `dict` (and `None`).

django-stubs/template/backends/base.pyi

@@ -2,7 +2,6 @@ from collections.abc import Iterator, Mapping
 from typing import Any, Protocol, type_check_only
 
 from django.http.request import HttpRequest
-from django.template.base import Context
 from django.utils.functional import cached_property
 from django.utils.safestring import SafeString
 
@@ -23,6 +22,6 @@ class BaseEngine:
 class _EngineTemplate(Protocol):
     def render(
         self,
-        context: Context | dict[str, Any] | None = ...,
+        context: dict[str, Any] | None = ...,
         request: HttpRequest | None = ...,
     ) -> SafeString: ...