Disable looking up snapshot versions in public repositories (apache#9336

)

- there isn't a need to lookup snapshots in public repositories
- this improves the Pulsar maven build since currently the build will attempt to lookup the snapshot versions of Pulsar modules from public repositories, for example:
Downloading from confluent: http://packages.confluent.io/maven/org/apache/pulsar/pulsar-client-original/2.8.0-SNAPSHOT/maven-metadata.xml
Downloading from central: https://repo1.maven.org/maven2/org/apache/pulsar/pulsar-client-original/2.8.0-SNAPSHOT/maven-metadata.xml
...

Co-authored-by: Sijie Guo <[email protected]>

pom.xml

@@ -1922,18 +1922,24 @@ flexible messaging model and an intuitive client API.</description>
       <id>central</id>
       <layout>default</layout>
       <url>https://repo1.maven.org/maven2</url>
-    </repository>
-    <repository>
       <snapshots>
         <enabled>false</enabled>
       </snapshots>
+    </repository>
+    <repository>
       <id>bintray-yahoo-maven</id>
       <name>bintray</name>
       <url>https://yahoo.bintray.com/maven</url>
+      <snapshots>
+        <enabled>false</enabled>
+      </snapshots>
     </repository>
     <repository>
       <id>confluent</id>
       <url>http://packages.confluent.io/maven/</url>
+      <snapshots>
+        <enabled>false</enabled>
+      </snapshots>
     </repository>
   </repositories>