Update Maven URL from HTTP to HTTPS

Since January 15, 2020 Maven Central no longer supports insecure communication over plain HTTP and requires that all requests to the repository are encrypted over HTTPS.

build.gradle

@@ -5,7 +5,7 @@ plugins {
 repositories {
     mavenLocal()
     maven {
-        url = 'http://repo.maven.apache.org/maven2'
+        url = 'https://repo.maven.apache.org/maven2'
     }
 }