fix: use future dates in checkpoint prune tests to prevent time-dependent failures (#5543)

The test_older_than tests in both JSON and SQLite prune suites used
hardcoded 2026-04-17 timestamps for the 'new' checkpoint. Once that
date passes, the checkpoint is older than 1 day and gets pruned along
with the 'old' one, causing assert count >= 1 to fail (count=0).

Use 2099-01-01 for the 'new' checkpoint so tests remain stable.

Co-authored-by: Joao Moura <joaomdmoura@gmail.com>

lib/crewai/tests/test_checkpoint_cli.py

@@ -292,7 +292,7 @@ class TestPruneJson:
                 d, name="20250101T000000_old01111_p-none.json"
             )
             os.utime(old_path, (0, 0))
-            _write_json_checkpoint(d, name="20260417T000000_new01111_p-none.json")
+            _write_json_checkpoint(d, name="20990101T000000_new01111_p-none.json")
             deleted = _prune_json(d, keep=None, older_than=timedelta(days=1))
             assert deleted == 1
 
@@ -330,7 +330,7 @@ class TestPruneSqlite:
         with tempfile.TemporaryDirectory() as d:
             db_path = os.path.join(d, "test.db")
             _create_sqlite_checkpoint(db_path, "20200101T000000_old01111")
-            _create_sqlite_checkpoint(db_path, "20260417T000000_new01111")
+            _create_sqlite_checkpoint(db_path, "20990101T000000_new01111")
             deleted = _prune_sqlite(db_path, keep=None, older_than=timedelta(days=1))
             assert deleted >= 1
             with sqlite3.connect(db_path) as conn: