vinyl: fix small run recovery

If run size is less than ALIGN_POS(sizeof(struct vy_run_info)), then
vy_range_recover() won't load it. This is due to a residue of aligned
read/write functionality, the rest of which was removed by commit
7fe24c42 ("All operation will be done over xlog. We don't need to use
aligned rw ops"). Remove this last ALIGN_POS. Steps to reproduce:

  space = box.schema.space.create("vinyl", { engine = 'vinyl' })
  space:create_index('primary', { parts = { 1, 'unsigned' } })
  space:insert({0})
  box.snapshot
  -- restart server
  space:select()