xfs: fix Sphinx documentation warning

Fix Sphinx documentation format warning by not indenting so much.

Documentation/admin-guide/xfs.rst:257: WARNING: Block quote ends without a blank line; unexpected unindent.
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

Documentation/admin-guide/xfs.rst

@@ -253,7 +253,7 @@ The following sysctls are available for the XFS filesystem:
 	pool.
 
   fs.xfs.speculative_prealloc_lifetime
-		(Units: seconds   Min: 1  Default: 300  Max: 86400)
+	(Units: seconds   Min: 1  Default: 300  Max: 86400)
 	The interval at which the background scanning for inodes
 	with unused speculative preallocation runs. The scan
 	removes unused preallocation from clean inodes and releases