ci: add back central repo for efficiency

When adding a custom repository, central repo inherited from Maven parent is tried last, instead of first.
This causes builds to be slower, as most dependencies are resolved via central.

pom.xml

@@ -55,10 +55,21 @@
     <module>deployment</module>
   </modules>
   <repositories>
+    <repository>
+      <id>central</id>
+      <name>Central Repository</name>
+      <url>https://repo.maven.apache.org/maven2</url>
+      <snapshots>
+        <enabled>false</enabled>
+      </snapshots>
+    </repository>
     <repository>
       <id>splunk</id>
       <name>Splunk Releases</name>
       <url>https://splunk.jfrog.io/splunk/ext-releases-local</url>
+      <snapshots>
+        <enabled>false</enabled>
+      </snapshots>
     </repository>
   </repositories>
   <dependencyManagement>