tune2fs: Remove support for clearing the SPARSE_SUPER feature

tune2fs: Remove support for clearing the SPARSE_SUPER feature

Clearing SPARSE_SUPER is dangerous; it can result in a filesystem
which e2fsck can't fix easily.  Since there is very few good reasons
for wanting to turn this feature off, disable tune2fs's abiity to do
this.  Users who really want this can use debugfs.

Also, deprecate the tune2fs -s option.  Remove it from the man page
and usage message.

Addresses-Sourceforge-Bug: #1840286

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>