Use https for the apache license

gradle.properties

@@ -7,7 +7,7 @@ POM_SCM_CONNECTION=scm:git:git://github.com/square/retrofit.git
 POM_SCM_DEV_CONNECTION=scm:git:ssh://git@github.com/square/retrofit.git
 
 POM_LICENCE_NAME=The Apache Software License, Version 2.0
-POM_LICENCE_URL=http://www.apache.org/licenses/LICENSE-2.0.txt
+POM_LICENCE_URL=https://www.apache.org/licenses/LICENSE-2.0.txt
 POM_LICENCE_DIST=repo
 
 POM_DEVELOPER_ID=square