fix _require_scratch_duperemove ordering

fix _require_scratch_duperemove ordering

Zorro complained that generic/559 stopped working, and I noticed that
the duperemove invocation in the _require_scratch_duperemove function
would fail with:

 Error 2: No such file or directory while getting path to file /opt/file1. Skipping.
 Error 2: No such file or directory while getting path to file /opt/file2. Skipping.
 No dedupe candidates found.
 Gathering file list...

The cause of this is the incorrect placement of _require_scratch_dedupe
after a _scratch_mount.  _require_scratch_dedupe formats, mounts, tests,
and unmounts the scratch filesystem, which means that it should not come
between a _scratch_mount call and code that uses $SCRATCH_MNT.

Cc: <fstests@vger.kernel.org> # v2024.12.22
Fixes: 3b9f5fc7d7d853 ("common: call _require_scratch_dedupe from _require_scratch_duperemove")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>