RTC_[D]CHECK_op: Remove "u" suffix on integer constants

There's no longer any need to make the two arguments have the same
signedness, so we can drop the "u" suffix on literal integer
arguments.

NOPRESUBMIT=true
BUG=webrtc:6645

Review-Url: https://codereview.webrtc.org/2535593002
Cr-Commit-Position: refs/heads/master@{#15280}

webrtc/modules/audio_coding/acm2/codec_manager.cc

@@ -211,7 +211,7 @@ bool CodecManager::MakeEncoder(RentACodec* rac, AudioCodingModule* acm) {
         if (sub_enc.empty()) {
           break;
         }
-        RTC_CHECK_EQ(1u, sub_enc.size());
+        RTC_CHECK_EQ(1, sub_enc.size());
 
         // Replace enc with its sub encoder. We need to put the sub encoder in
         // a temporary first, since otherwise the old value of enc would be