Revert "[Feed] Stop obfuscation of FeedRefreshTask class name."

This reverts commit 6205ad09.

Reason for revert: Not needed now that https://chromium-review.googlesource.com/c/1371244 landed.

Original change's description:
> [Feed] Stop obfuscation of FeedRefreshTask class name.
> 
> Bug: 913696
> Change-Id: I29fe62f4022c464330385c9e6e4d3253f2f3273c
> Reviewed-on: https://chromium-review.googlesource.com/c/1370555
> Reviewed-by: Filip Gorski <fgorski@chromium.org>
> Commit-Queue: Sky Malice <skym@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#615356}

TBR=fgorski@chromium.org,skym@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 913696
Change-Id: I99720fe10cc3f292e44e0da72387585f685326bd
Reviewed-on: https://chromium-review.googlesource.com/c/1374451Reviewed-by: Filip Gorski <fgorski@chromium.org>
Commit-Queue: Sky Malice <skym@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616068}

chrome/android/feed/core/java/src/org/chromium/chrome/browser/feed/FeedRefreshTask.java

@@ -8,7 +8,6 @@ import android.content.Context;
 
 import org.chromium.base.ContextUtils;
 import org.chromium.base.ThreadUtils;
-import org.chromium.base.annotations.UsedByReflection;
 import org.chromium.chrome.browser.background_task_scheduler.NativeBackgroundTask;
 import org.chromium.components.background_task_scheduler.BackgroundTaskScheduler;
 import org.chromium.components.background_task_scheduler.BackgroundTaskSchedulerFactory;
@@ -22,7 +21,6 @@ import java.util.concurrent.TimeUnit;
  * A task implementation that loads native and then tries to refresh the Feed's articles. Failures
  * or interruptions are not retried or rescheduled.
  */
-@UsedByReflection("BackgroundTaskReflection.java")
 public class FeedRefreshTask extends NativeBackgroundTask {
     // The amount of "flex" to add around the fetching periods, as a ratio of the period.
     private static final double FLEX_FACTOR = 0.1;