fix(occ): Suppress errors when checking config.php fileowner

[provokateurin]

Summary

In a docker container of mine I've seen that I'm unable to install since #33545:

+ ./occ maintenance:install --admin-pass admin --admin-email [email protected]

Warning: fileowner(): stat failed for /usr/src/nextcloud/config/config.php in /usr/src/nextcloud/occ on line 20
An unhandled exception has been thrown:
Exception: Config file has leading content, please remove everything before "<?php" in apcu.config.php in /usr/src/nextcloud/lib/private/Config.php:222
Stack trace:
#0 /usr/src/nextcloud/lib/private/Config.php(40): OC\Config->readData()
#1 /usr/src/nextcloud/lib/base.php(94): OC\Config->__construct('/usr/src/nextcl...')
#2 /usr/src/nextcloud/lib/base.php(615): OC::initPaths()
#3 /usr/src/nextcloud/lib/base.php(1156): OC::init()
#4 /usr/src/nextcloud/console.php(28): require_once('/usr/src/nextcl...')
#5 /usr/src/nextcloud/occ(33): require_once('/usr/src/nextcl...')
#6 {main}

I have never seen it fail locally, but I have seen a few times that if something goes wrong in occ, odd errors are thrown down the line.
I tried this patch in the docker container and it makes it successfully install again.
I'm quite surprised, that I didn't find any reports about this issue in the server or docker repos.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[provokateurin]

/backport to stable31

[provokateurin]

/backport to stable30

[susnux]

looks good

[szaimen]

LGTM but didnt test