Settings: Remove the crawler sleep time setting.

src/indexing/EventIndex.js

@@ -30,6 +30,7 @@ export default class EventIndex {
         // The time in ms that the crawler will wait loop iterations if there
         // have not been any checkpoints to consume in the last iteration.
         this._crawlerIdleTime = 5000;
+        this._crawlerSleepTime = 3000;
         // The maximum number of events our crawler should fetch in a single
         // crawl.
         this._eventsPerCrawl = 100;
@@ -211,7 +212,7 @@ export default class EventIndex {
             // This is a low priority task and we don't want to spam our
             // homeserver with /messages requests so we set a hefty timeout
             // here.
-            let sleepTime = SettingsStore.getValueAt(SettingLevel.DEVICE, 'crawlerSleepTime');
+            let sleepTime = this._crawlerSleepTime;
 
             // Don't let the user configure a lower sleep time than 100 ms.
             sleepTime = Math.max(sleepTime, 100);