Reduce web WHOIS error log level to warning

There's not much we can do when the user sends incorrect HTTP requests or cannot finish SSL handshake (the problematic requests are likely from bots anyway). Reducing the log level to warning in order to reduce spamming.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=207159118

java/google/registry/proxy/handler/WebWhoisRedirectHandler.java

@@ -135,7 +135,7 @@ public class WebWhoisRedirectHandler extends SimpleChannelInboundHandler<HttpReq
 
   @Override
   public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
-    logger.atSevere().withCause(cause).log(
+    logger.atWarning().withCause(cause).log(
         (isHttps ? "HTTPS" : "HTTP") + " WHOIS inbound exception caught for channel %s",
         ctx.channel());
     ChannelFuture unusedFuture = ctx.close();