Fix deprecated actions and make release

[matthiaskoenig]

https://github.com/matthiaskoenig/sbmlsim/runs/1806370939?check_suite_focus=true

Number opened for PR is null
Error: Unable to process command '::set-env name=PULL_REQUEST_NUMBER::null' successfully.
Error: The `set-env` command is disabled. Please upgrade to using Environment Files or opt into unsecure command execution by setting the `ACTIONS_ALLOW_UNSECURE_COMMANDS` environment variable to `true`. For more information see: https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/
Error: Unable to process command '::set-env name=PULL_REQUEST_RETURN_CODE::0' successfully.
Error: The `set-env` command is disabled. Please upgrade to using Environment Files or opt into unsecure command execution by setting the `ACTIONS_ALLOW_UNSECURE_COMMANDS` environment variable to `true`. For more information see: https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/
Error: Unable to process command '::set-env name=PULL_REQUEST_URL::null' successfully.
Error: The `set-env` command is disabled. Please upgrade to using Environment Files or opt into unsecure command execution by setting the `ACTIONS_ALLOW_UNSECURE_COMMANDS` environment variable to `true`. For more information see: https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/