Removes some repositories from the build.

We really didn't need those. Might as well keep it clean.

library/build.gradle

@@ -8,26 +8,12 @@
  * limitations under the License.
  */
 
-import org.apache.tools.ant.taskdefs.condition.Os
-
-import java.nio.file.Files
-
-buildscript {
-    repositories {
-        jcenter()
-        google()
-    }
-}
-
 plugins {
     id "java-library"
 }
 
 repositories {
-    google()
     jcenter()
-    mavenCentral()
-    maven { url 'https://jitpack.io' }
     maven {
         url  "https://dl.bintray.com/jmonkeyengine/org.jmonkeyengine"
     }