Docs mention removed release creation script

In doc/core/ctu_can_fd_architecture.lyx line 1441 "RTL release can be created by following script:" and onward references scripts/create_release.py removed in 10b5a64e. gitlab-runner exec shell pages is sadly not a replacement as it fails on cp: cannot stat 'test/rtl_lst.txt': No such file or directory which needs to be created earlier in the pipeline, and gitlab-runner doesn't seem to support running a pipeline or multiple stages locally. Unfortunately, the user should be probably informed to download the release from gitlab instead.