Don't backup views

[Michal-Leszczynski]

Backing up views doesn't make any sense as the advised way to restore them is by recreating them on restored table. This would require to first validate that the base table is even being backed up. Checking which tables are views and which are not can currently be done only via cql session. It might be available via scylla client if scylladb/scylladb#17958 is implemented.

cc: @karol-kokoszka @tzach

[karol-kokoszka]

Candidate for 3.2.9 (or 3.3.1)

[karol-kokoszka]

grooming notes

SM doesn't restore views using SSTables. It just recreates them. There is complete no need of backing them up.

We must drop the backup of views and explicitly inform about it in the documentation.