Update comment on why Switch Access can't be enabled from signin page

TBR=dmazzoni@chromium.org

AX-Relnotes: n/a.
Bug: None.
Change-Id: I69a8229f75647608efbb96f8b5632925b18d0300
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391591Reviewed-by: Anastasia Helfinstein <anastasi@google.com>
Commit-Queue: Anastasia Helfinstein <anastasi@google.com>
Cr-Commit-Position: refs/heads/master@{#804028}

ash/accessibility/accessibility_controller_impl.cc

@@ -1073,8 +1073,8 @@ bool AccessibilityControllerImpl::IsSwitchAccessRunning() const {
 }
 
 bool AccessibilityControllerImpl::IsSwitchAccessSettingVisibleInTray() {
-  // Switch Access cannot be enabled on the sign-in page until crbug/1108808 has
-  // been fully resolved.
+  // Switch Access cannot be enabled on the sign-in page because there is no way
+  // to configure switches while the device is locked.
   if (!switch_access().enabled() &&
       Shell::Get()->session_controller()->login_status() ==
           ash::LoginStatus::NOT_LOGGED_IN) {