Remove ISpiderLoader from docs and tests.

docs/news.rst

@@ -2643,7 +2643,7 @@ Deprecation removals
     (:issue:`6109`, :issue:`6116`)
 
 -   A custom class assigned to the :setting:`SPIDER_LOADER_CLASS` setting that
-    does not implement the :class:`~scrapy.interfaces.ISpiderLoader` interface
+    does not implement the ``ISpiderLoader`` interface
     will now raise a :exc:`zope.interface.verify.DoesNotImplement` exception at
     run time. Non-compliant classes have been triggering a deprecation warning
     since Scrapy 1.0.0.

docs/topics/api.rst

@@ -178,9 +178,7 @@ SpiderLoader API
     defined across the project.
 
     Custom spider loaders can be employed by specifying their path in the
-    :setting:`SPIDER_LOADER_CLASS` project setting. They must fully implement
-    the :class:`scrapy.interfaces.ISpiderLoader` interface to guarantee an
-    errorless execution.
+    :setting:`SPIDER_LOADER_CLASS` project setting.
 
     .. method:: from_settings(settings)
 

tests/test_spiderloader/__init__.py

@@ -5,14 +5,12 @@ from pathlib import Path
 from unittest import mock
 
 import pytest
-from zope.interface.verify import verifyObject
 
 # ugly hack to avoid cyclic imports of scrapy.spiders when running this test
 # alone
 import scrapy
 from scrapy.crawler import CrawlerRunner
 from scrapy.http import Request
-from scrapy.interfaces import ISpiderLoader
 from scrapy.settings import Settings
 from scrapy.spiderloader import DummySpiderLoader, SpiderLoader, get_spider_loader
 
@@ -45,9 +43,6 @@ def spider_loader(spider_loader_env):
 
 
 class TestSpiderLoader:
-    def test_interface(self, spider_loader):
-        verifyObject(ISpiderLoader, spider_loader)
-
     def test_list(self, spider_loader):
         assert set(spider_loader.list()) == {
             "spider1",