test/boost/mutation_test: remove v1 specific test code
test/boost/mutation_test: remove v1 specific test code

From test_compactor_range_tombstone_spanning_many_pages, preparing for
the retirement of the v1 output of the compactor.

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla