Revert "Update includes for webrtc/{base => rtc_base} rename (1/3)"

This reverts commit c8fa692ec44fd6ba4fa3d085ac3161a262fc18c5.

BUG=webrtc:7634
NOTRY=True
NOPRESUBMIT=True

Review-Url: https://codereview.webrtc.org/2964773002 .
Cr-Commit-Position: refs/heads/master@{#18872}

webrtc/modules/rtp_rtcp/test/testAPI/test_api.cc

@@ -14,8 +14,8 @@
 #include <memory>
 #include <vector>
 
-#include "webrtc/rtc_base/checks.h"
-#include "webrtc/rtc_base/rate_limiter.h"
+#include "webrtc/base/checks.h"
+#include "webrtc/base/rate_limiter.h"
 #include "webrtc/test/null_transport.h"
 
 namespace webrtc {