Make the URL in Slack notification for check_bitrise_ios_release_tag public

Currently the url points to the jenkins jobs and it is not accessible outside of the M4, additionally, it does not work there unless you are in Jenkins. 
We should have it accessible without connecting to the Mac and to Jenkins.

See for example:
https://mozilla.slack.com/archives/C08096YAV09/p1771436526433469