reject_conflict_paths: add missing docstring

Status Job ID Name Coverage
  External
passed ghostflow-check-master

passed rust-git-checks-rustdash-linux-debug

passed rust-git-checks-rustdash-linux-debug+latest

failed rust-git-checks-rustdash-linux-debug+minver

passed rust-git-checks-rustdash-linux-debug

00:00:27

passed rust-git-checks-rustdash-linux-debug+latest

00:00:26

failed rust-git-checks-rustdash-linux-debug+minver

00:00:04