chore(issues): remove all of Organization Activity (#74587)

This has been marked deprecated since March
#67315

All affected organizations have been
[notified](https://www.notion.so/sentry/Notice-of-Organization-Activity-Endpoint-Deprecation-4b4d3edb2c954669a0b1358570d)
back then.

src/sentry/api/urls.py

@@ -116,7 +116,6 @@
 from sentry.issues.endpoints import (
     ActionableItemsEndpoint,
     GroupEventsEndpoint,
-    OrganizationActivityEndpoint,
     OrganizationGroupIndexEndpoint,
     OrganizationGroupSearchViewsEndpoint,
     OrganizationReleasePreviousCommitsEndpoint,
@@ -1328,11 +1327,6 @@ def create_group_urls(name_prefix: str) -> list[URLPattern | URLResolver]:
         OrganizationAccessRequestDetailsEndpoint.as_view(),
         name="sentry-api-0-organization-access-request-details",
     ),
-    re_path(
-        r"^(?P<organization_id_or_slug>[^\/]+)/activity/$",
-        OrganizationActivityEndpoint.as_view(),
-        name="sentry-api-0-organization-activity",
-    ),
     re_path(
         r"^(?P<organization_id_or_slug>[^\/]+)/api-keys/$",
         OrganizationApiKeyIndexEndpoint.as_view(),

src/sentry/issues/endpoints/__init__.py

@@ -1,6 +1,5 @@
 from .actionable_items import ActionableItemsEndpoint
 from .group_events import GroupEventsEndpoint
-from .organization_activity import OrganizationActivityEndpoint
 from .organization_group_index import OrganizationGroupIndexEndpoint
 from .organization_group_search_views import OrganizationGroupSearchViewsEndpoint
 from .organization_release_previous_commits import OrganizationReleasePreviousCommitsEndpoint
@@ -11,7 +10,6 @@
 __all__ = (
     "ActionableItemsEndpoint",
     "GroupEventsEndpoint",
-    "OrganizationActivityEndpoint",
     "OrganizationGroupIndexEndpoint",
     "OrganizationGroupSearchViewsEndpoint",
     "OrganizationReleasePreviousCommitsEndpoint",