Fix AudioLevel print-out in rtc_event_log2text

uint8_t was being printed as a char; a conversion to int was necessary.

Bug: None
Change-Id: I4c6875c693350b95b8742a6a8e17157743db62cb
Reviewed-on: https://webrtc-review.googlesource.com/17400
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Commit-Queue: Elad Alon <eladalon@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20502}

logging/rtc_event_log/rtc_event_log2text.cc

@@ -485,7 +485,8 @@ int main(int argc, char* argv[]) {
                       << parsed_header.extension.transmissionTimeOffset;
           }
           if (parsed_header.extension.hasAudioLevel) {
-            std::cout << "\tAudioLevel=" << parsed_header.extension.audioLevel;
+            std::cout << "\tAudioLevel=" <<
+                static_cast<int>(parsed_header.extension.audioLevel);
           }
           std::cout << std::endl;
         }