increase netty version to 4.1.48 (AsyncHttpClient#1713)

Addresses the issue described in netty/netty#10111

Author: dmjb

pom.xml

@@ -465,7 +465,7 @@
     <surefire.redirectTestOutputToFile>true</surefire.redirectTestOutputToFile>
     <source.property>1.8</source.property>
     <target.property>1.8</target.property>
-    <netty.version>4.1.46.Final</netty.version>
+    <netty.version>4.1.48.Final</netty.version>
     <slf4j.version>1.7.30</slf4j.version>
     <reactive-streams.version>1.0.3</reactive-streams.version>
     <activation.version>1.2.0</activation.version>