python: remove linkify-changelog reference as it now lives in root

python/helper-scripts/README.md

@@ -1,6 +1,5 @@
 These scripts automate some tasks related to release process.
 
 * __`relicence.py`__ rewrites licence headers in all non-empty Python files
-* __`linkify-changelog.py`__ generates Markdown links to github issues/PRs in changelog
 * __`bump-required-fw-versions.py`__ downloads latest firmware versions and updates trezorlib requirements
 * __`make-options-rst.py`__ runs all `trezorctl` commands with the `--help` option and concatenates output as `OPTIONS.rst`