fix(notify-irm): remove ${{ }} templates from description blocks

[DevSecNinja]

Summary

Every consumer of notify-irm is failing at action-load time with:

DevSecNinja/.github/.../actions/notify-irm/action.yml (Line: 3, Col: 14):
Unrecognized function: 'always'.
Located at position 1 within expression: always() && github.ref == 'refs/heads/main' && github.event_name == 'push'

Root cause

GitHub Actions runs the template engine over action.yml in full — including the description: block. The usage example I embedded in the description contained ${{ always() && github.ref == ... }}, and always() is only valid in workflow if: contexts. The engine rejected the expression and refused to load the manifest, so every workflow that did uses: DevSecNinja/.github/.github/actions/notify-irm@<sha> failed.

Fix

• Strip all ${{ }} expressions out of description: blocks in action.yml.
• Move the usage example into a sibling README.md (where it can use ${{ }} freely because it isn't templated).

Verification

• runs.steps[0] still uses ${{ inputs.* }} and ${{ github.* }} — those are valid in composite steps and were never the problem.
• After this lands, downstream consumers (truenas-apps#306 and dotfiles#255) will load the action successfully and their existing SHA pins (a877d352…) only need to be bumped to the merge SHA of this PR.