docs(admin): correct the antivirus Stream Length default

The Daemon (Socket) section states 10485760 bytes, ten megabytes. The actual
default in files_antivirus is 26214400 (25 MiB), per AV_STREAM_MAX_LENGTH in
lib/AppInfo/ConfigLexicon.php.

AI-Assisted-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: Anna Larch <anna@nextcloud.com>

Author: miaulalala

admin_manual/configuration_server/antivirus_configuration.rst

@@ -146,7 +146,7 @@ Daemon (Socket)
   .. figure:: ../images/antivirus-daemon-socket.png
 
   The ``Stream Length`` value sets the number of bytes read in one pass.
-  10485760 bytes, or ten megabytes, is the default. This value should be
+  26214400 bytes, or 25 MiB, is the default. This value should be
   no larger than the PHP ``memory_limit`` settings, or physical memory if
   ``memory_limit`` is set to -1 (no limit).