Lower max number of JobScheduler IDs.

Some devices can only handle 25 job IDs, so I lowered it to 20.

src/org/thoughtcrime/securesms/jobmanager/JobSchedulerScheduler.java

@@ -25,7 +25,7 @@ public class JobSchedulerScheduler implements Scheduler {
   private static final String PREF_NAME    = "JobSchedulerScheduler_prefs";
   private static final String PREF_NEXT_ID = "pref_next_id";
 
-  private static final int MAX_ID = 75;
+  private static final int MAX_ID = 20;
 
   private final Application application;