Fix -Wextra-semi warnings.

Starting from https://chromium-review.googlesource.com/c/1485012,
-Wextra-semi is enabled and WebRTC has some violations to fix.

This is a follow-up of https://webrtc-review.googlesource.com/c/123560.

Bug: webrtc:10355
Change-Id: I012b7497fc8991037fd77aa98f1579c22e08206f
Reviewed-on: https://webrtc-review.googlesource.com/c/124126
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26831}

modules/audio_coding/acm2/audio_coding_module_unittest.cc

@@ -1484,7 +1484,7 @@ const std::string payload_checksum =
         "ab88b1a049c36bdfeb7e8b057ef6982a",
         "27fef7b799393347ec3b5694369a1c36",
         "27fef7b799393347ec3b5694369a1c36");
-};  // namespace
+}  // namespace
 
 TEST_F(AcmSenderBitExactnessOldApi, Opus_stereo_20ms) {
   ASSERT_NO_FATAL_FAILURE(SetUpTest("opus", 48000, 2, 120, 960, 960));