generic/135: don't try to rm $SCRATCH_MNT/*

generic/135: don't try to rm $SCRATCH_MNT/*

This fixes a regression for ext4 introduced by commit 32e14cb90b88
("fstests: don't use directory stacks"), which replaced a number of
files at the top-level of the scratch file system:

    async_file sync_file direct_file trunc_file

with "rm $SCRATCH_MNT/*".  This causes a test failure on ext4 file
systems caused by a failed attempt to unlink the lost+found directory.
The thing, is these files are all super small (4k or 16k) and the
scratch file system is going to get reformatted before it gets used
again.  So just dropping the delete is the simplest way to solve the
problem.

Fixes: 32e14cb90b88 ("fstests: don't use directory stacks")
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>