[stable19] Clarify PHP warning in admin settings

[backportbot-nextcloud]

backport of #22766

[faily-bot]

🤖 beep boop beep 🤖

Here are the logs for the failed build:

Status of 32936: failure

mysql8.0-php7.2

Show full log

There were 2 warnings:

1) Test\Files\ViewTest::testRenameFailDeleteTargetKeepSource
Trying to configure method "writeStream" which cannot be configured because it does not exist, has not been specified, is final, or is static

2) Test\Files\ViewTest::testCopyFailDeleteTargetKeepSource
Trying to configure method "writeStream" which cannot be configured because it does not exist, has not been specified, is final, or is static

--

There was 1 failure:

1) OCA\Files_Versions\Tests\VersioningTest::testRestoreMovedShare
File content has not changed
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'version 2'
+'version 1'

/drone/src/apps/files_versions/tests/VersioningTest.php:730