Fix `if_not_else` wrong unmangled macros

[profetia]

Closes rust-lang/rust-clippy#15924

changelog: [if_not_else] fix wrongly unmangled macros

[rustbot]

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[rustbot]

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[profetia]

r? clippy

[profetia]

r? clippy

[dswij]

Thank you!