Issuer keys directory's permission group should not be set to 'xrootd'

[h2zh]

Pelican Service:

• Client
• Plugin
• Registry
• Director
• Origin
• Cache
• Other (please give the detail)

We used to need xrootd to read the public key, which might be the reason why we set the permission group
of issuer keys directory to xrootd (see here for the code). However, we have shifted to use the web UI to get public key (by accessing /.well-known/openid-configuration) a long time ago. There is no necessity to keep this group permission setting anymore.

This issue is a sibling issue of #2056