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}
diff --git a/webrtc/modules/audio_coding/neteq/test/RTPencode.cc b/webrtc/modules/audio_coding/neteq/test/RTPencode.cc
index 4ccf4fb..f390f53 100644
--- a/webrtc/modules/audio_coding/neteq/test/RTPencode.cc
+++ b/webrtc/modules/audio_coding/neteq/test/RTPencode.cc
@@ -1724,7 +1724,7 @@
 #ifdef CODEC_OPUS
     cdlen = WebRtcOpus_Encode(opus_inst[k], indata, frameLen, kRtpDataSize - 12,
                               encoded);
-    RTC_CHECK_GT(cdlen, 0u);
+    RTC_CHECK_GT(cdlen, 0);
 #endif
     indata += frameLen;
     encoded += cdlen;