Update policy.rs - small typo in error message

[matthiasdebernardini]

Small typo

Description

Notes to the reviewers

Changelog notice

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran cargo fmt and cargo clippy before committing

New Features:

• I've added tests for the new feature
• I've added docs for the new feature

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[notmandatory]

As a policy we don't accept PRs without a bit more significant changes, just to reduce PR noise. Can you please add this as a comment on #1028 and I'll get it fixed there. Thanks!

[notmandatory]

Also @realeinherjar has #1165 which will auto check new PRs for spelling errors and should prevent this sort of typo. :-)