custom_check: Remove assertEquals check.

Ruff checks this as U005 (and even auto-fixes it).

Signed-off-by: Anders Kaseorg <anders@zulip.com>

tools/linter_lib/custom_check.py

@@ -276,12 +276,6 @@ python_rules = RuleList(
             "good_lines": ["def foo (self):"],
             "bad_lines": ["def foo(self: Any):"],
         },
-        {
-            "pattern": "assertEquals[(]",
-            "description": "Use assertEqual, not assertEquals (which is deprecated).",
-            "good_lines": ["assertEqual(1, 2)"],
-            "bad_lines": ["assertEquals(1, 2)"],
-        },
         {
             "pattern": r"assertEqual[(]len[(][^\n ]*[)],",
             "description": "Use the assert_length helper instead of assertEqual(len(..), ..).",