Drop the manual compaction step

We already compact the local DB on each write, so this should be
unneccessary. It is also causing crashes on some lower power devices,
presumably because it's holding open some transaction for too long and
erroring everything out after that.

#5348

webapp/src/js/bootstrapper/purger.js

@@ -303,14 +303,6 @@ module.exports = function(DB, userCtx, initialReplication) {
 
   const p = Promise.resolve()
     .then(() => begin(userCtx))
-    .then(count => {
-      if (count) {
-        publish('optimise');
-        return DB.compact().then(() => count);
-      } else {
-        return count;
-      }
-    })
     .then(count => publish('done', {totalPurged: count}));
 
   p.on = (type, callback) => {