Replace RTC_DCHECK(false) with RTC_NOTREACHED().

Bulk of changes done using

  git grep -l 'RTC_DCHECK(false)' | \
    xargs sed -i 's/RTC_DCHECK(false)/RTC_NOTREACHED()/'

peerconnection.cc also used RTC_DCHECK(false && "msg") in two places,
which were updated manually.

BUG=webrtc:6424

Review-Url: https://codereview.webrtc.org/2623313004
Cr-Commit-Position: refs/heads/master@{#16026}

webrtc/sdk/android/src/jni/androidnetworkmonitor_jni.cc

@@ -84,7 +84,7 @@ static rtc::AdapterType AdapterTypeFromNetworkType(NetworkType network_type) {
       // Map it to VPN for now.
       return rtc::ADAPTER_TYPE_VPN;
     default:
-      RTC_DCHECK(false) << "Invalid network type " << network_type;
+      RTC_NOTREACHED() << "Invalid network type " << network_type;
       return rtc::ADAPTER_TYPE_UNKNOWN;
   }
 }