fix(user): note legacy ownCloud name for OWNCLOUD_CRITICAL_FREE_SPACE_BYTES

fix(user): note legacy ownCloud name for OWNCLOUD_CRITICAL_FREE_SPACE_BYTES

AI-Assisted-By: claude-sonnet-4-6 <noreply@anthropic.com>

Signed-off-by: Anna Larch <anna@nextcloud.com>

[skip ci]

Author: miaulalala

admin_manual/desktop/envvars.rst

@@ -8,7 +8,7 @@ The environment variables are:
 
 - `OWNCLOUD_CHUNK_SIZE` (default: 5242880; 5 MiB) – Specifies the chunk size of uploaded files in bytes. Increasing this value may help with synchronization problems in certain configurations.  
 - `OWNCLOUD_TIMEOUT` (default: 300 s) – The timeout for network connections in seconds.
-- `OWNCLOUD_CRITICAL_FREE_SPACE_BYTES` (default: 512\*1000\*1000 bytes) - The minimum disk space needed for operation. A fatal error is raised if less free space is available. 
+- `OWNCLOUD_CRITICAL_FREE_SPACE_BYTES` (default: 512\*1000\*1000 bytes) - The minimum disk space needed for operation. A fatal error is raised if less free space is available.
 - `OWNCLOUD_FREE_SPACE_BYTES` (default: 1000\*1000\*1000 bytes) - Downloads that would reduce the free space below this value are skipped. More information available under the "Low Disk Space" section. 
 - `OWNCLOUD_MAX_PARALLEL` (default: 6) - Maximum number of parallel jobs. 
 - `OWNCLOUD_BLACKLIST_TIME_MIN` (default: 25 s) - Minimum timeout for blacklisted files.