Revert "Update includes for webrtc/{base => rtc_base} rename (2/3)"

This reverts commit c3771cc4d37f5573fe53b7c7cff295a4f0f9560f.
(breaks downstream internal project)

BUG=webrtc:7634
NOTRY=True
NOPRESUBMIT=True

Review-Url: https://codereview.webrtc.org/2972463002 .
Cr-Commit-Position: refs/heads/master@{#18873}

webrtc/rtc_tools/event_log_visualizer/plot_base.cc

@@ -12,7 +12,7 @@
 
 #include <algorithm>
 
-#include "webrtc/rtc_base/checks.h"
+#include "webrtc/base/checks.h"
 
 namespace webrtc {
 namespace plotting {