xfs: Remove duplicate assert statement in xfs_bmap_btalloc()

The check for verifying if the allocated extent is from an AG whose
index is greater than or equal to that of tp->t_firstblock is already
done a couple of statements earlier in the same function. Hence this
commit removes the redundant assert statement.

Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_bmap.c

@@ -3699,7 +3699,6 @@ xfs_bmap_btalloc(
 		ap->blkno = args.fsbno;
 		if (ap->tp->t_firstblock == NULLFSBLOCK)
 			ap->tp->t_firstblock = args.fsbno;
-		ASSERT(nullfb || fb_agno <= args.agno);
 		ap->length = args.len;
 		/*
 		 * If the extent size hint is active, we tried to round the