HBASE-28949 Remove the netty 3 dependency management section (apache#6460)

Signed-off-by: Nihal Jain <nihaljain@apache.org>
(cherry picked from commit 31593cc)

Author: Apache9

pom.xml

@@ -566,7 +566,6 @@
       in the dependencyManagement section as it could still lead to different versions of netty
       modules and cause trouble if we only rely on transitive dependencies.
     -->
-    <netty3.version>3.10.6.Final</netty3.version>
     <netty4.version>4.1.112.Final</netty4.version>
     <!-- end HBASE-15925 default hadoop compatibility values -->
     <audience-annotations.version>0.13.0</audience-annotations.version>
@@ -1583,11 +1582,6 @@
           </exclusion>
         </exclusions>
       </dependency>
-      <dependency>
-        <groupId>io.netty</groupId>
-        <artifactId>netty</artifactId>
-        <version>${netty3.version}</version>
-      </dependency>
       <dependency>
         <groupId>io.netty</groupId>
         <artifactId>netty-bom</artifactId>