assistant: remove deprecated comment

We are checking locales in |IsAssistantAllowedForProfile|.

Bug: None
Test: None
Change-Id: I2c6e5cfdbc8f23c48b646d89c92e0ed9aa2f8899
Reviewed-on: https://chromium-review.googlesource.com/c/1371817Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Xiaohui Chen <xiaohuic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615671}

chromeos/chromeos_switches.cc

@@ -681,7 +681,6 @@ bool IsAssistantFlagsEnabled() {
 }
 
 bool IsAssistantEnabled() {
-  // TODO(xiaohuic): We will add locale restrictions later.
   return IsAssistantFlagsEnabled();
 }