HADOOP-18602. Remove netty3 dependency

LICENSE-binary

@@ -260,7 +260,6 @@ io.grpc:grpc-netty:1.26.0
 io.grpc:grpc-protobuf:1.26.0
 io.grpc:grpc-protobuf-lite:1.26.0
 io.grpc:grpc-stub:1.26.0
-io.netty:netty:3.10.6.Final
 io.netty:netty-all:4.1.77.Final
 io.netty:netty-buffer:4.1.77.Final
 io.netty:netty-codec:4.1.77.Final

hadoop-hdfs-project/hadoop-hdfs/pom.xml

@@ -175,11 +175,6 @@ https://maven.apache.org/xsd/maven-4.0.0.xsd">
       <artifactId>slf4j-log4j12</artifactId>
       <scope>provided</scope>
     </dependency>
-    <dependency>
-      <groupId>io.netty</groupId>
-      <artifactId>netty</artifactId>
-      <scope>compile</scope>
-    </dependency>
     <dependency>
       <groupId>io.netty</groupId>
       <artifactId>netty-all</artifactId>

hadoop-project/pom.xml

@@ -140,7 +140,6 @@
     <grizzly.version>2.2.21</grizzly.version>
     <gson.version>2.9.0</gson.version>
     <metrics.version>3.2.4</metrics.version>
-    <netty3.version>3.10.6.Final</netty3.version>
     <netty4.version>4.1.77.Final</netty4.version>
     <snappy-java.version>1.1.8.2</snappy-java.version>
     <lz4-java.version>1.7.1</lz4-java.version>
@@ -1000,13 +999,6 @@
         </exclusions>
       </dependency>
 
-
-      <dependency>
-        <groupId>io.netty</groupId>
-        <artifactId>netty</artifactId>
-        <version>${netty3.version}</version>
-      </dependency>
-
       <dependency>
         <groupId>io.netty</groupId>
         <artifactId>netty-all</artifactId>