generic/747: redirect mkfs stderr to seqres.full

generic/747: redirect mkfs stderr to seqres.full

ext4 fails on this test with:

  --- /tmp/fstests/tests/generic/747.out	2024-05-13 06:05:59.727025928 -0700
  +++ /var/tmp/fstests/generic/747.out.bad	2024-05-21 18:34:51.836000000 -0700
  @@ -1,4 +1,5 @@
   QA output created by 747
  +mke2fs 1.47.2~WIP-2024-05-21 (21-May-2024)
   Starting fillup using direct IO
   Starting mixed write/delete test using direct IO
   Starting mixed write/delete test using buffered IO

The reason for this is that mke2fs annoyingly prints the program version
to stderr, which messes up the golden output.  Fix this by redirecting
stderr like all the othe tests, even though this doesn't seem like a
great solution...

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Zorro Lang <zlang@kernel.org>