sstables: change summary_la to summary_ka
sstables: change summary_la to summary_ka

What we implement is ka, not la. Since the summary is the one element that
actually changed in the 2.2 implementation, it is particularly important that
we get this one right. I have previously missed this.

Signed-off-by: Glauber Costa <f8b79557d19b40666ebe336545a0b6178af65685@cloudius-systems.com>

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