Delete access tokens on user delete (#34036)

Trying to delete a user record from our admin panel throws the following
error:

`update or delete on table "users" violates foreign key constraint
"access_tokens_user_id_fkey" on table "access_tokens"
Detail: Key (id)=(....) is still referenced from table "access_tokens".`

We need to add a cascade delete to the `access_tokens` table.

Release Notes:

- N/A

crates/collab/migrations.sqlite/20221109000000_test_schema.sql

@@ -26,7 +26,7 @@ CREATE UNIQUE INDEX "index_users_on_github_user_id" ON "users" ("github_user_id"
 
 CREATE TABLE "access_tokens" (
     "id" INTEGER PRIMARY KEY AUTOINCREMENT,
-    "user_id" INTEGER REFERENCES users (id),
+    "user_id" INTEGER REFERENCES users (id) ON DELETE CASCADE,
     "impersonated_user_id" INTEGER REFERENCES users (id),
     "hash" VARCHAR(128)
 );