clippy_utils: Make sym_helper module private

[BD103]

This is a small PR that makes clippy_utils::sym_helper private. Since this module only contains a single macro, sym!, which is already re-exported at the root with #[macro_export], there's no need for the module to be public.

changelog: none

• cargo test passes locally
• Run cargo dev fmt

[rustbot]

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[rustbot]

☔ The latest upstream changes (possibly cc00c77) made this pull request unmergeable. Please resolve the merge conflicts.

[Manishearth]

Merge conflicts need to be fixed

[y21]

The conflicting PR #14650 removed the sym! macro and the sym_helper module along with it, so I don't think there is anything that could be done here anymore

[Manishearth]

Ah. Thanks for your efforts in this PR, sorry it's no longer necessary!

[Manishearth]

@y21 heh, I was wondering what would cause a one liner to conflict, but I couldn't see the conflicts on mobile

[BD103]

Ah. Thanks for your efforts in this PR, sorry it's no longer necessary!

No worries! :)