db: Fix include in cell_name.hh
db: Fix include in cell_name.hh

Fix the following build error:

  In file included from ./db/cell.hh:29:0,
                   from ./db/expiring_cell.hh:26,
                   from cql3/attributes.hh:31,
                   from cql3/cql3.cc:33:
  ./db/composites/cell_name.hh: At global scope:
  ./db/composites/cell_name.hh:51:36: error: expected class-name before ‘{’ token
   class cell_name : public composite {
                                    ^
  ninja: build stopped: subcommand failed.

Signed-off-by: Pekka Enberg <add4fcd06328a394f0ad91feda7ee057316dc5ed@cloudius-systems.com>

respu/scylla,stamhe/scylla,wildinto/scylla,aruanruan/scylla,scylladb/scylla,capturePointer/scylla,phonkee/scylla,gwicke/scylla,aruanruan/scylla,asias/scylla,linearregression/scylla,kjniemi/scylla,acbellini/scylla,eklitzke/scylla,duarten/scylla,linearregression/scylla,acbellini/scylla,wildinto/scylla,kangkot/scylla,justintung/scylla,victorbriz/scylla,scylladb/scylla,justintung/scylla,senseb/scylla,respu/scylla,bowlofstew/scylla,stamhe/scylla,shaunstanislaus/scylla,gwicke/scylla,eklitzke/scylla,scylladb/scylla,phonkee/scylla,raphaelsc/scylla,rluta/scylla,guiquanz/scylla,tempbottle/scylla,avikivity/scylla,duarten/scylla,kjniemi/scylla,acbellini/scylla,shaunstanislaus/scylla,capturePointer/scylla,senseb/scylla,rluta/scylla,scylladb/scylla,kangkot/scylla,bowlofstew/scylla,bowlofstew/scylla,glommer/scylla,guiquanz/scylla,rentongzhang/scylla,justintung/scylla,dwdm/scylla,victorbriz/scylla,victorbriz/scylla,gwicke/scylla,glommer/scylla,duarten/scylla,linearregression/scylla,eklitzke/scylla,capturePointer/scylla,phonkee/scylla,guiquanz/scylla,rentongzhang/scylla,tempbottle/scylla,kjniemi/scylla,rluta/scylla,avikivity/scylla,rentongzhang/scylla,dwdm/scylla,senseb/scylla,respu/scylla,raphaelsc/scylla,tempbottle/scylla,asias/scylla,aruanruan/scylla,kangkot/scylla,wildinto/scylla,asias/scylla,shaunstanislaus/scylla,raphaelsc/scylla,stamhe/scylla,avikivity/scylla,dwdm/scylla,glommer/scylla