try to fix gradle build

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1855972 13f79535-47bb-0310-9956-ffa450edef68

build.gradle

@@ -103,10 +103,10 @@ subprojects {
     sourceCompatibility = 1.8
 
     repositories {
+        mavenCentral()
         maven {
             url 'https://repository.apache.org/content/repositories/staging'
         }
-        mavenCentral()
     }
 
     jar {