gh-99518: Fix escape symbol in test_enum

[sobolevn]

It should be fine now :)

CC @ethanfurman

• Issue: Buildbot failure: unhandled warning in test_enum.py #99518

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @sobolevn for commit a8ae4b2 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.

[sobolevn]

There are two unrelated failures. Others are fine!