Remove duplicated speech_monitor.* entried from build

speech_monitor.{cc/h} were being included in both "browser_tests" and
"test_support" targets in //chrome/test. Given that the tests depend on
test_support, this CL removes the files there and relies on the build
dependency.

Change-Id: Ia6f4d993ffd0e156c5f665f18377e34f51e3a9f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2617844Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Henrique Ferreiro <hferreiro@igalia.com>
Cr-Commit-Position: refs/heads/master@{#841657}

chrome/test/BUILD.gn

@@ -2409,8 +2409,6 @@ if (!is_android) {
         "../browser/chromeos/accessibility/magnification_controller_browsertest.cc",
         "../browser/chromeos/accessibility/magnification_manager_browsertest.cc",
         "../browser/chromeos/accessibility/select_to_speak_browsertest.cc",
-        "../browser/chromeos/accessibility/speech_monitor.cc",
-        "../browser/chromeos/accessibility/speech_monitor.h",
         "../browser/chromeos/accessibility/spoken_feedback_app_list_browsertest.cc",
         "../browser/chromeos/accessibility/spoken_feedback_browsertest.cc",
         "../browser/chromeos/accessibility/spoken_feedback_browsertest.h",