fix: empty_enum renamed to empty_enums

[canmi21]

Motivation

  ⎿  warning: lint `clippy::empty_enum` has been renamed to `clippy::empty_enums`                                               
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       = help: use the new name `clippy::empty_enums`  

Solution

empty_enum -> empty_enums

[canmi21]

Idk why the test cancelled. It seems because I modified the clippy lint rule :(

[jplatte]

Nah, just GitHub Actions having an outage yesterday.

[canmi21]

review need