fix some misspelling

[Abirdcfly]

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

[serathius]

I think such typo fixes should be accompanied with adding static analysis that would prevent them from happening in the future. Without it we will be just repeatably make the same mistakes again and again.

@Abirdcfly I assume that you used some tool to find those typos, maybe you would consider integrating it as part of our testing?

[stale]

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