Update maven repo to https

From Jan 15, 2020 Maven Central Repository no longer supports HTTP and requires that all requests to the repository are encrypted over HTTPS.
https://support.sonatype.com/hc/en-us/articles/360041287334

Change-Id: I41c120a417eb26b06141bf8cdf6f573e3cd76515
diff --git a/pom.xml b/pom.xml
index 54e6b35..bf02e6e 100644
--- a/pom.xml
+++ b/pom.xml
@@ -60,7 +60,7 @@
         <repository>
             <id>central</id>
             <name>Central Repository</name>
-            <url>http://repo.maven.apache.org/maven2</url>
+            <url>https://repo.maven.apache.org/maven2</url>
             <layout>default</layout>
             <snapshots>
                 <enabled>false</enabled>