remove unnecessary 1 second sleep from user_sup terminate

[tsloughter]

I talked to @jhogberg a bit ago and he believed this wait was not necessary because the buffer was handled elsewhere.

If there is a good way to test this, aside from just if the current tests pass, I'm willing to add a test.

I'm still trying to get checks to build locally, but figured I'd open this since I meant to open it weeks ago :)

[github-actions]

CT Test Results

    2 files     74 suites   1h 5m 20s ⏱️
1 775 tests 1 361 ✅ 413 💤 1 ❌
2 027 runs  1 555 ✅ 471 💤 1 ❌

For more details on these failures, see this check.

Results for commit 62eecb8.

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[lpil]

Very happy to see this change! 🎉

[garazdawi]

That sleep was added in R7B, which is way before we added synchronous writing to io. It should have been removed when we did that, but must have been missed.

[bjorng]

With this PR, the test case run_erl_SUITE:heavy/1 in the system "application" fails.

[garazdawi]

#10808 is a version that may fix the testcase.

[tsloughter]

Great! I'll close mine.