Revert "Prevent repeated keys from providing output in learn mode"

This reverts commit 6c45baae.

Reason for revert: <INSERT REASONING HERE>
Need to stop propagation of key events even if they are repeated.

Original change's description:
> Prevent repeated keys from providing output in learn mode
> 
> R=​akihiroota@chromium.org
> 
> Fixed: 1106462
> AX-Relnotes: only announce a modifier once, when holding down modifiers like Search in ChromeVox Learn Mode.
> Change-Id: Iaa9de466462450ccef889a2b789b0c150127c814
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2308489
> Reviewed-by: Akihiro Ota <akihiroota@chromium.org>
> Commit-Queue: David Tseng <dtseng@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#790193}

TBR=dtseng@chromium.org,akihiroota@chromium.org

Change-Id: I4d2646397a765a6e78b11dd2ebdd777ed45be8ef
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2309563Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790223}

chrome/browser/resources/chromeos/accessibility/chromevox/learn_mode/kbexplorer.js

@@ -72,9 +72,6 @@ KbExplorer = class {
       ChromeVox.tts.stop();
     }
     KbExplorer.keydownWithoutKeyupEvents_.add(evt.keyCode);
-    if (evt.repeat) {
-      return false;
-    }
     ChromeVox.tts.speak(
         KeyUtil.getReadableNameForKeyCode(evt.keyCode),
         window.backgroundWindow.QueueMode.QUEUE,